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... space for a variety of reasons. Overall motivations for renumbering
are discussed in [RFC2071]. This document deals with the router-
related aspects of a renumbering effort, once the decision to
renumber has been made.
...
... This document deals with planning and implementation guidelines for
the interconnection devices of an enterprise. Of these devices,
routers have the clearest association with the IP numbering plan ...
... Section 7.
6. Evaluate the specific router mechanisms that will be affected
by renumbering. See Sections 8 through 13.
...
... for such planning are in Section 15.
When trying to understand the interactions of renumbering on routers,
remember there different aspects to the problem, depending on the
scope of the renumbering involved. Remember that even an
...
... vendor-independent.
Not all features discussed, of course, have been implemented on all
routers. This document should not be used as a general comparison
of the richness of features of different implementations.
...
... routing).
While this document is titled "Router Renumbering Guide," it
recognizes that renumbering may be required due to the initial
installation of routers ...
... Router Renumbering Guide," it
recognizes that renumbering may be required due to the initial
installation of routers in a bridged legacy network. Organizations
...
... may have had an adequate bridging solution that did not scale with
growth. Some organizations could not able to move to routers until
router forwarding performance ...
... growth. Some organizations could not able to move to routers until
router forwarding performance improved [Carpenter] to be comparable
...
... Layer 3 devices. A workgroup switch product often includes a router
function, so the numbering plan must support both flat Layer 2 ...
... VCs.
These often have a significant performance impact on the router, and
may be less reliable because a single point of failure is created.
...
... 1. A desire not to use VLSM. This is often founded in fear
rather than technology.
2. Router implementation issues that limit the number of subnets
or interfaces ...
... subnets
or interfaces a given router can support.
3. An inherently point-to-multipoint application (e.g., remote
...
... services affects the addressing
structure and routers, it is worth reviewing what would appear to be
very basic concepts of IP subnets. The traditional view is that a
...
... destination is on a different subnet, and it is assumed that
router intervention is needed to reach it.
The first NBMA ...
... replication usually causes an
appreciable CPU load in the replicating router. The replicating
router also is a single point of failure for the subnet ...
... CPU load in the replicating router. The replicating
router also is a single point of failure for the subnet. This method
...
... In a routing protocol, such as OSPF, that has a concept of designated
routers, explicit configuration usually is needed. Other problems in
using a meshed subnet is that all VCs ...
... VCs may not have the same
performance, but the router cannot prefer individual paths within the
subnet.
...
...
These access server functions may be part of the software of a
"router" and thus are within the scope of this Guide.
The preferred technique [Hubbard ...
... destination is on a different subnet than the source, the cut-through
typically is to the egress router that serves the destination subnet.
...
... The advantage of cut-through in such a case is that it avoids the
latency of multiple router hops, and reduces load on "backbone"
routers ...
... router hops, and reduces load on "backbone"
routers. The cut-through decision is usually made by an entry router
that is aware of both the routed and switched environments.
...
... backbone"
routers. The cut-through decision is usually made by an entry router
that is aware of both the routed and switched environments.
...
... that is aware of both the routed and switched environments.
This entry router communicates with a address resolution server using
the Next Hop Resolution Protocol ...
... address to either a next-hop
router (where cut-through is not appropriate) or to an egress router
reached over the switched service ...
... next-hop
router (where cut-through is not appropriate) or to an egress router
reached over the switched service. Obviously, the data base ...
... numbering plan? To understand the general
problem, it can be worthwhile to review the basic principles of
routers. While most readers will have a good intuitive sense of
this, the principles have refined in the current usage of IP.
...
... destination address. The
sequence of bits examined by the router always begin at the left of
the address (i.e., the most significant bit ...
... bits are assigned by an outside organization.
The router looks up the prefix in its routing table (formally called
...
... Forwarding Information Base). If the prefix is in the routing
table, the router then selects an outgoing interface that will take
the routed packet to the next hop ...
... If the prefix cannot be found in the routing table, the router
returns an ICMP Destination Unreachable message to the source address ...
... Assuming the prefix is found in the routing table, the router then
transmits the datagram through the indicated outgoing interface ...
...
From the router renumbering perspective, renumbering impact is apt to
be greatest in highly connected parts of "backbones," and least in
...
...
In this drawing, assume Back1 and Back2 exchange full routes; Back1
is also the exterior router. Regional routers (Reg) exchange full
routes with one another and aggregate addresses ...
... In this drawing, assume Back1 and Back2 exchange full routes; Back1
is also the exterior router. Regional routers (Reg) exchange full
routes with one another and aggregate addresses to the backbone ...
... routers. Branch routers default to regional routers.
From a pure topological standpoint, the higher in the hierarchy, the
...
... "subnets." It is critical to realize that routers make routing
decisions based on the total prefix ...
... prefix of interest, regardless of who
controls which bits. In other words, the router really doesn't know
or care about subnet boundaries.
...
... subnets into a single network
number advertisement sent to external routers. In a more general
way, we now think of extending the prefix to the right as subnetting
...
... 1) Inadvertent alteration or deletion of external addresses
as part of router reconfiguration.
2) Loss of connectivity to application servers inside the
...
...
Renumbering affects both the configuration of specific router
"boxes," and the overall system of routers ...
... Renumbering will have the least impact when the minimum number of
reconfiguration options are needed. When planning renumbering on
routers, consider that many existing configurations may contain
hard-coded IP addresses that may not be necessary, even if
...
... hard-coded IP addresses that may not be necessary, even if
renumbering were not to occur. Part of a router renumbering effort
should include, wherever possible, replacing router mechanisms based
...
... renumbering were not to occur. Part of a router renumbering effort
should include, wherever possible, replacing router mechanisms based
on hard-coded addresses with more flexible mechanisms.
...
... Renumbering will also generally be easier if the configuration
changes can be made offline on appropriate servers, and then
downloaded to the router if the router implementation permits.
...
... configuration
changes can be made offline on appropriate servers, and then
downloaded to the router if the router implementation permits.
...
... well-known method for reducing the amount of reference by one
router to other routers is to use a default route to a higher-level,
...
... method for reducing the amount of reference by one
router to other routers is to use a default route to a higher-level,
better-connected router ...
... routers is to use a default route to a higher-level,
better-connected router. This assumes a hierarchical network design,
which is generally desirable in the interest of scaling.
...
... Server References in Routers ...
...
Routers commonly communicate with an assortment of network management
and other infrastructural servers. Examples of these servers are
...
... DNS name rather
than by IP address. If a specific router implementation only
supports explicit address references, this should be documented as
...
... Domain Name Service is a powerful tool in any renumbering effort,
and can help routers as well as end hosts. If traceroute displays
...
... Be aware that dynamically learned names and addresses may be cached
in router tables. For a router to learn changes in address to name
...
... addresses may be cached
in router tables. For a router to learn changes in address to name
correspondence, it may be necessary to restart ...
... address to name
correspondence, it may be necessary to restart the router or
explicitly clear the cache.
...
... require coordination when changing providers.
Commonly, router renumbering goes through a transition period.
During this transition, old and new addresses may coexist in the
...
... addresses for periods of days.
If, for example, a given router interface may have a coexisting new
and old address, it can be appropriate to introduce the new address ...
... tools to
renumber DNS names for router addresses, by putting a comment (e.g.,
";newaddr") at the end of the A statements for the new addresses ...
... Care should be taken to assure that PTR reverse mapping entries are
defined for new addresses, because some router vendor tools depend on
reverse mapping.
...
... address assignment is especially
attractive for end hosts, and routers may play a key role in this
process. Routers ...
... routers may play a key role in this
process. Routers may act as servers and actually assign addresses,
or may be responsible for forwarding end host ...
... address assignment, however, is
also used to assign IP addresses to router interfaces. An address
assignment server may assign an IP address to a router ...
... router interfaces. An address
assignment server may assign an IP address to a router either in the
usual DHCP way, based on a MAC address ...
... usual DHCP way, based on a MAC address in the router, or simply based
on the physical connectivity of the new router ...
... router, or simply based
on the physical connectivity of the new router. In other words, any
router connected on a specific interface ...
... physical connectivity of the new router. In other words, any
router connected on a specific interface of the configuring router
...
... router connected on a specific interface of the configuring router
would be assigned the same IP address.
...
... DHCP servers. If the server is not on the same medium as
the end hosts, routers may need to play a role in establishing
connectivity between the end host ...
... client is not on the same medium as the address assignment
server, routers either must act as address assignment services, or
...
... broadcasts to the location of appropriate servers.
If the router acts as an address assignment server, its database of
...
... addresses that it can assign may change during renumbering. If the
router forwards to a DHCP or BOOTP server, it must know the address ...
... services.
When the router contains assignable addresses, these may need to
change as part of renumbering. Alternatively, hard-coded references
...
... Router Autoonfiguration ...
... address only for a
single connection (i.e., between the new and configuring routers).
The newly assigned address may then be used to "bootstrap ...
... address may then be used to "bootstrap" a full
configuration into the new router.
Dynamic address assignment ...
...
Dynamic address assignment to routers is probably most common at
outlying "stub" or "edge" routers ...
... routers is probably most common at
outlying "stub" or "edge" routers that connect via WAN links to a
...
...
When such autoconfiguration is used on edge routers, it may be
necessary to force a restart of the edge router ...
... edge routers, it may be
necessary to force a restart of the edge router after renumbering.
Restarting may be the only way to force the autoconfigured router ...
... edge router after renumbering.
Restarting may be the only way to force the autoconfigured router to
learn its new address. Other out-of-band ...
... Potential Pitfalls in Router Renumbering ...
...
This ideal, unfortunately, is not understood by a significant number
of routers (and terminal access servers that participate in routing),
...
... addressing. If CIDR rules have been followed in address
assignment, then steps need to be taken to assure the router
understands them, or appropriate steps need to be taken to interface
...
... CIDR-compliant.
Some routers support classless routing without further
configuration, other routers ...
... routers support classless routing without further
configuration, other routers support classless routing but require
specific configuration steps to enable it, while other routers ...
... routers support classless routing but require
specific configuration steps to enable it, while other routers only
understand classful routing. In general, most renumbering will
...
... eventually require classless routing support. It is essential to
know if a given router can support classless routing. If it does
not, workarounds may be possible. Workarounds are likely to be
...
... 1879 that CIDR compliance rules must be
enabled explicitly in some routers, while other routers do not
understand CIDR ...
... CIDR compliance rules must be
enabled explicitly in some routers, while other routers do not
understand CIDR rules.
...
...
Another problem that can occur with routers or routing mechanisms
that do not understand arbitrary length prefix ...
... addresses were in 172.31.0.0/16.
Assume a RIPv1 system of three routers:
10.1.0.1/16 10.2.0.1/16
...
... | |
+-------------------------------------+
| Router 1 |
+-------------------------------------+
| 172.31.1.1/24
...
... | 172.31.1.2/24
+-------------------------------------+
| Router 2 |<------OUTSIDE
+-------------------------------------+
| 172.31.2.1/24
...
... | 172.31.2.2/24
+-------------------------------------+
| Router 3 |
+-------------------------------------+
| |
...
... 10.3.0.1/16 10.4.0.1/16
Router 1 can reach its two locally connected subnets, 10.1.0.0/16 and
10.2.0.0/16. It will aggregate them into a single announcement of
...
... interface.
In like manner, Router 3 can reach its two locally connected subnets,
0.3.0.0/16 and 10.4.0.0/16. It will aggregate them into a single
...
... interface.
When Router 2 receives a packet from its "outside" interface
destined, say, to 10.1.1.56/16, where does it send it? Router ...
... Router 2 receives a packet from its "outside" interface
destined, say, to 10.1.1.56/16, where does it send it? Router 2 has
received two advertisements of 10.0.0.0 on different interfaces,
...
... interfaces,
without any detail of subnets inside 10.0.0.0. Router 2 has an
ambiguous routing table in terms of the next hop ...
... subnets.
Two problems occur in this configuration. Router 2 does not know
where to send outside packets destined for a subnet of 10.0.0.0.
...
... where to send outside packets destined for a subnet of 10.0.0.0.
Connectivity, however, also will break between Routers 1 and 3,
because Router 2 does not know the next hop ...
... Connectivity, however, also will break between Routers 1 and 3,
because Router 2 does not know the next hop for any subnet of
...
... alternative would be to establish an IP-over-IP tunnel through Router
2, and give this a subnet in 10.0.0.0. This additional subnet ...
... subnet in 10.0.0.0. This additional subnet would
be visible only in Routers 1 and 3. It would solve the connectivity
problem between Routers 1 and 3, but Router ...
... be visible only in Routers 1 and 3. It would solve the connectivity
problem between Routers 1 and 3, but Router 2 would still not be able
to forward outside packets. This might be a perfectly acceptable
...
... Routers 1 and 3. It would solve the connectivity
problem between Routers 1 and 3, but Router 2 would still not be able
to forward outside packets. This might be a perfectly acceptable
solution if Router ...
... Router 2 would still not be able
to forward outside packets. This might be a perfectly acceptable
solution if Router 2 is simply being used to connect two parts of
10.0.0.0.
...
... directly to the ARP. If the destination is not, the router will
respond as if it were the destination, and the originating host ...
... datagram to the router. Once the datagram is in the router,
the VLSM-aware router can forward it.
...
... subnet. All other traffic is sent to a
hard-coded default router address. In such cases, workarounds may be
needed to force the host ...
... hosts.
Hosts that only understand default routers also are apt only to
understand classful addressing. If the host ...
... destinations can be forwarded there. While RIPv1 does not
support arbitrary prefixes, the router(s) issuing the routing updates
may have additional capabilities that let them correctly forward such
...
... traffic. The priority, therefore, is to get the non-local routers to
a router that understands the overall routing ...
... addresses as a DHCP client, this may become more common. When a
router so acquires addresses, care must be taken that the MAC address
...
... DHCP server is in fact unique.
Modern routers usually support protocol architectures besides IP.
...
... Network Services, and IPX, may modify MAC addresses of routers such
that a given MAC address appears on more than one interface ...
... Dynamic protocol mechanisms that to some extent depend on IP
addresses may be affected by router renumbering. These include
mechanisms that assign or resolve addresses (e.g., DHCP ...
... cache
IP addresses. When the router is renumbered, these servers may point
to old addresses. Certain proxy server ...
... addresses. Certain proxy server functions may reside on
routers, and the router may need to be restarted to reset the cache.
...
... proxy server functions may reside on
routers, and the router may need to be restarted to reset the cache.
...
... endpoints of TCP tunnels terminating on routers may be internally
identified by address/port ...
... prefix has the same number of bits as the old
external part, requiring no change to subnetting, the router part of
renumbering may be fairly simple. If the router configurations are
...
... external part, requiring no change to subnetting, the router part of
renumbering may be fairly simple. If the router configurations are
available in machine-readable form, as text files or parsable SNMP
...
...
It is worthwhile to distinguish that a router's use of a DNS name
does not necessarily mean that name is defined in a name server ...
... does not necessarily mean that name is defined in a name server.
Routers often contain static address to name mappings local to the
router ...
... Routers often contain static address to name mappings local to the
router, so both the DNS zone files and the router configurations will
...
... DNS, RR in a zone file outside
ours), the definition statement (or equivalent if the routers are
configured with SNMP), and current IP address ...
... address coexistence work.
If, for example, a given router interface may have a coexisting new
and old address, it can be appropriate to introduce the new address ...
... tools to
renumber DNS names for router addresses, by putting a comment (e.g.,
";newaddr") at the end of the CNAME ...
... Care should be taken to assure that PTR reverse mapping entries are
defined for new addresses, because some router vendor tools depend on
reverse mapping.
...
... Router Identifiers ...
... physical or virtual interfaces on a single router. They also include
commands that assign IP-address-related information to the router ...
... router. They also include
commands that assign IP-address-related information to the router
"box" itself, and commands which involve the router's interaction
...
... IP-address-related information to the router
"box" itself, and commands which involve the router's interaction
with neighbors below the full routing ...
... Global Router Identification ...
...
Traditional IP routers do not have unique identifiers, but rather are
treated as collections of IP addresses ...
...
address for the router itself, typically to establish tunnel
endpoints between peer routers. Other applications include
...
... address for the router itself, typically to establish tunnel
endpoints between peer routers. Other applications include
"unnumbered interfaces" used to conserve address space ...
... | |
+-------------------------------------+
| Router 1 |
| |
| 10.1.0.1/16 |
...
... | 172.31.1.2/24 # | 172.31.2.2/24
+-------------------#-----------------+
| Router 2 |
| |
| 10.1.0.2/16 |
...
... 172.31.5.1/24 172.31.6.1/24
A common practice to provide router identifiers is using the "highest
IP address ...
... identifiers is using the "highest
IP address" on the router as an identifier for the "box." Many
implementations have a default mechanism to establish the router ID ...
... router as an identifier for the "box." Many
implementations have a default mechanism to establish the router ID,
which may be the highest configured address, or the highest active ...
... address.
Typical applications of a global router ID may not require it be a
"real" IP address that is advertised through the routing ...
... is simply a 32-bit identifier local to each router. When this is the
case, this identifier can come from the RFC 1918 ...
... address space.
Allowing default selection of the router ID can be unstable and is
not recommended. Most implementations have a means of declaring a
pseudo ...
... established for the entire set of interface addresses on a router.
This allows testing, telnet, etc., to the router ...
... Interface addresses are perhaps the most basic place to begin router
renumbering. Interface configuration will require an IP address ...
... specified. This will be especially common on older host-based
routers.
Multiple IP addresses ...
... same interface. This is often a valuable technique in renumbering,
because the router interface can be configured to respond to both the
new and old addresses.
...
... taken in removing the old addresses. Some router implementations
have special meaning to the order of address declarations on an
...
... address declarations on an
interface. It is highly likely that routers, or at least the
interface, must be restarted after an address ...
... subnet space on serial links. One mechanism is to implement
proprietary "half-router" schemes, in which the unnumbered link
between router ...
... router" schemes, in which the unnumbered link
between router pairs is treated as an "internal bus" creating a
"virtual router," such that the scope of the unnumbered interface ...
... between router pairs is treated as an "internal bus" creating a
"virtual router," such that the scope of the unnumbered interface is
limited to the pair of routers ...
... virtual router," such that the scope of the unnumbered interface is
limited to the pair of routers.
| +------------+ +------------+ |
...
... | +------------+ +------------+
In the above example, software in routers R1 and R2 automatically
forward every packet received on serial interface ...
... S0 or E0. Some management is possible as long as at least one IP
address on the router (e.g., E0) is reachable, since this will permit
SNMP connectivity to the router ...
... router (e.g., E0) is reachable, since this will permit
SNMP connectivity to the router. Once the router is reachable with
SNMP ...
... SNMP connectivity to the router. Once the router is reachable with
SNMP, the unnumbered interface ...
... address for every unnumbered interface on a router. In the above
example, R1 would use 10.1.0.1 as its identifier ...
... difficulties. If there are multiple unnumbered interfaces on a
router, which one (if any) should/will respond to a ping? Other
network management ...
... RFC1918 private address space. Inter-router links rarely need to be
accessed from the Internet ...
...
If unnumbered interfaces are kept, and the router-ID convention is
used, it will probably be more stable to rely on an explicitly
configured router ID ...
... router-ID convention is
used, it will probably be more stable to rely on an explicitly
configured router ID rather than a default from a numbered interface
address ...
... LAN MAC addresses is usually done
automatically by the router software, there will be cases where
special mappings may be needed. For example, the MAC address used by
...
... special mappings may be needed. For example, the MAC address used by
router interfaces may be locally administered (i.e., set manually),
rather than relying on the burnt-in hardware address. It may be part
...
...
RFC1812prop specifies that router interfaces MUST NOT forward limited
broadcasts (i.e., to the all-ones destination address ...
... DNS or DHCP) by sending limited broadcasts. Router
interfaces can cope with this situation by translating the limited
broadcast address ...
... or PPP. In a renumbering effort, several kinds of changes may made
to be made on routers participating in dynamic addressing.
...
... Apple MacIP.
If the router does not assign addresses, it may be responsible for
forwarding address assignment ...
... congestion.
Routers may implement logging of filtering events, typically denial
of access. If logging is implemented, logging servers to which log
...
...
Router filters typically contain some number of include/exclude rules
that define which packets to include in forwarding and which to
...
... critical components of firewall systems.
Architecturally, two router functions are described in firewall
models, the external screening router ...
... router functions are described in firewall
models, the external screening router between the outside and the
"demilitarized zone (DMZ)," and the internal screening router between
...
... models, the external screening router between the outside and the
"demilitarized zone (DMZ)," and the internal screening router between
the inside and the "perimeter network." Between these two networks ...
... address space (i.e., visible to the
Internet) changes, this will mean that the outside screening router
will need configuration changes. Since the outside screening router ...
... router
will need configuration changes. Since the outside screening router
may be under the control of the ISP rather than the entrerprise,
...
... From | External | | +--------+ |---| Internal |
Internet...| Screening |---| +--------+ | | Screening |
| Router | |---| Bastion|------| | Router |....To
+-----------+ | | Host ...
... Internet...| Screening |---| +--------+ | | Screening |
| Router | |---| Bastion|------| | Router |....To
+-----------+ | | Host | | +-----------+ Internal
...
... | +--------+ | +-----------+
External screening routers typically have inbound access lists that
block unauthorized traffic from the Internet ...
... the external screening host also will need to change. Internal
screening routers permit access from the internal network to selected
servers on the perimeter network ...
... itself. If the enterprise uses private address space internally,
renumbering may not affect this router.
Another component of a firewall ...
... RADIUS and TACACS+, may
insert dynamically assigned access rules into router configurations.
For example, a RADIUS database ...
...
Configuration information dynamically communicated to the router may
be in the form of filtering rules. Effectively, this authentication ...
... authentication
database becomes an extension of the router configuration database.
Both these databases ...
... dynamic configuration issue arises when "stateful packet
screening" on bastion hosts or routers is used to provide security
for UDP ...
... lifetime of a single packet response. If these
rules are defined in a database outside of the router, the rule
database again is an extension of router ...
... router, the rule
database again is an extension of router configuration that must be
part of the renumbering effort.
...
... address of static
routes may need to change. It may be necessary to restart routers or
explicitly clear a routing table entry to force the changed static
...
... hosts, where it may be used as a method
of router discovery, or for load-balancing and fault tolerance when
multiple routers are on a subnet ...
... of router discovery, or for load-balancing and fault tolerance when
multiple routers are on a subnet. In these applications, RIP need
...
... OSPF has several sensitivities to renumbering beyond those of simpler
routing protocols. If router IDs are assigned to be part of the
registered address space, they may need to be changed as part of the
...
...
address space for router IDs, as long as these can be looked up in a
DNS server within the domain ...
... OSPF costs can be assigned to different VCs,
designated router configuration is not needed, etc.
...
... autonomous system number," which need not be a true
AS number but simply identifies a set of cooperating routers, must be
the same on the IGRP and EIGRP processes for automatic redistribution
to occur.
...
... IGRP and EIGRP can be used to advertise external routes.
Renumbering that affects BGP-speaking routers can be complex, because
it can require changes not only in the BGP routers of the local
...
... Renumbering that affects BGP-speaking routers can be complex, because
it can require changes not only in the BGP routers of the local
Autonomous System, but also require changes in routers ...
... BGP routers of the local
Autonomous System, but also require changes in routers of other AS
and in routing registries ...
... routing usually will have
routing information not only in their routers, but in databases
operated by registries ...
... tools exist [RtConfig] for generating policy configuration part
of BGP router configuration statements from the policies specified in
RIPE-181 or RPSL.
...
...
This section is intended to deal with those parts of network
management that are intimately associated with routers, rather than a
general discussion of renumbering and network management ...
... interfaces, virtual interfaces, and router IDs of routers. Remember
that it is perfectly acceptable to identify internal interfaces ...
... interfaces, virtual interfaces, and router IDs of routers. Remember
that it is perfectly acceptable to identify internal interfaces with
...
...
Also remember that some name resolution may be done by static tables
that are part of router configurations. Changing the DNS entries,
and even restarting ...
...
Performance information can be recorded in routers themselves, and
retrieved by network management scripts. Other performance ...
... SNMP manager or other management
applications may periodically poll accounting information in routers,
and thus contain hard-coded IP addresses.
...
... filtering, and
access control. Routers can have hard-coded references to servers
for any of these functions.
...
... for any of these functions.
In addition, routers commonly will contain filters containing
security ...
...
Much of the effort in renumbering will be on platforms other than
routers. Nevertheless, routers are a key part of any renumbering
effort.
...
... Much of the effort in renumbering will be on platforms other than
routers. Nevertheless, routers are a key part of any renumbering
effort.
...
... network renumberings,
possibly with secondary addresses on core routers? Is NAT
appropriate? If so, how is it to be used?
...
... Clear caches as appropriate.
Remember static name definitions in routers may not be affected
by DNS changes.
...
... networks. For changes to take effect, it is likely that at least
interfaces and probably routers will have to be restarted. The
sequence in which changes are applied must be carefully thought out,
to avoid loss of connectivity, routing loops ...
... undergone renumbering have had to pay careful attention to informing
users of possible outages, coordinating changes among multiple sites,
etc. It will be an organization-specific decision whether router
renumbering can be implemented incrementally or must be done in a
major "flag day" conversion.
...
... major "flag day" conversion.
Before making significant changes, TAKE BACKUPS FIRST of all router
configuration files, DNS zone ...
...
Operationally, an important part of renumbering and continued
numbering maintenance is not to rely on local router interfaces,
either command language interpreter, menu-based, or graphic, for the
...
...
Once the configuration file is defined for a router, mechanisms for
loading it vary with the specific router implementation. In general,
...
... configuration file is defined for a router, mechanisms for
loading it vary with the specific router implementation. In general,
these will include a file transfer using FTP ...