Quick Notes: EIGRP Named Mode (CCIE Official Cert Guide: Chapter 8)

From: CCIE Routing and Switching v5.0 Official Cert Guide, Volume 1, 5th Edition

EIGRP Named Mode

  • Starting with IOS Release 15.0(1)M.
  • Earlier implementation configured EIGRP processes directly by their AS numbers separately for IPv4 and IPv6, also called the classic mode or the autonomous system mode.
  • The named mode is preferred.
  • The classic mode remains for backwards compatibility.
  • The reason for the update was to produce a better unified and more consistent configuration interface.
  • A single EIGRP process configuration consists of one or more address family sections, each of them specifying details of EIGRP operation for the particular address family.
  • Even former per-interface commands are within the context of the named mode.
  • The entire EIGRP configuration is located in a single place.
  • If an EIGRP instance is configured in named mode, all EIGRP commands outside the named mode will be ignored.
  • The classic mode and named mode are just two different ways of how EIGRP is configured. They do not constitute two different versions of EIGRP.
  • Three building blocks:
  1. Address Family (AF) section: Mandatory section that specifies the particular address family for which an EIGRP instance shall be started. The autonomous system number is part of the AF section.
  2. Per-AF-interface section: Optional section holds EIGRP settings pertaining to the specified interface and AF. One per-AF-interface section can be created for each routed interface or subinterface. In case both af-interface default and a specific af-interface define the same setting, the interface-specific section is preferred.
  3. Per-AF-topology section: A section presented inside a particular AF, related to the support of Multi Topology Routing (MTR) in EIGRP. The topology base will always be present in the configuration, even if the IOS has no support for multiple routing topologies.

router eigrp CCIE
 address-family ipv4 unicast autonomous-system 1
   af-interface default
     hello-interval 1
     hold-time 3
   af-inteface Loopback0
   topology base
     maximum-paths 6
     variance 4
 address-family ipv6 unicast autonomous-system 1
   af-interface default
   af-interface Loopback0
     no shutdown
   af-interface FastEthernet0/0
     no shutdown
   topology base
     timers active-time 1

  • As soon as the IPv6 EIGRP address family is configured, it immediately runs on all IPv6-enabled interfaces.
  • The named mode is entered using the router eigrp <name> command, where <name> is an arbitrary text name (a virtual instance name) of the EIGRP process.
  • The process name is not sent in EIGRP messages; it is locally significant value and is never compared to process names on other routers.
  • Each named EIGRP process can hold only a single instance for an address family.
  • If it is necessary to run two IPv4 EIGRP instances (for example, AS number 1 and AS number 64512), each of them must be placed into a separate EIGRP process with a unique name.
  • Also, two or more distinct named EIGRP processes cannot run the same address family instance with the same AS number.
  • One-to-one correspondence between an EIGRP named process and an address family instance with a particular AS number.
  • The AS numbers for individual address families in the same EIGRP process do not need to match.
  • In the classic mode, an IPv6 EIGRP process was shut down by default after configuring it, and no shutdown was necessary to actually start it.
  • In the named mode, the opposite is true. As soon as IPv6 address family is configured, it automatically adopts all interfaces on which IPv6 has been enabled (even link-local addresses).
  • Typically, use the af-interface default to first keep the IPv6 address family instance off all interfaces, and only activate it on selected interfaces later.
  • Notice the difference between passive-interface default and af-interface default shutdown.
  • passive-interface: no EIGRP adjacencies will be formed, but its global prefixes will still be advertised over other interfaces.
  • shutdown: completely igonored by EIGRP, not forming any adjacencies over it and also not advertising any of its prefixes.

Address Family Section

  • Configurations specific to the EIGRP process itself.
  • Commonly used commands include network and neighbor statements.

Address Family configuration commands:
  • af-interface: enter Address Family interface configuration.
  • default: set a command to its defaults.
  • eigrp: EIGRP Address Family specific commands.
  • exit-address-family:exit Address Family configuration mode.
  • help: description of the interactive help system.
  • maximum-prefix: maximum number of prefixes acceptable in aggregate.
  • metric: modify metrics and parameters for advertisement.
  • neighbor: specify an IPv4 neighbor router.
  • network: enable routing on an IP network.
  • shutdown: shutdown address family.
  • timers: adjust peering based timers.
  • topology: topology configuration mode.

Per-AF-interface Configuration Section

  • EIGRP interface-specific commands are applied, except bandwidth and delay.
  • No summary-address command under the default interface.

Address Family Interfaces configuration commands:
  • add-paths: advertise add paths.
  • authentication: authentication subcommands.
  • bandwidth-percent: set percentage of bandwidth percentage limit.
  • bfd: enable Bidirectional Forwarding Detection.
  • dampening-change: percent interface metric must change to cause update.
  • dampening-interval: time in seconds to check interface metrics.
  • default: set a command to its defaults.
  • exit-af-interface: exit from Address Family Interface configuration mode.
  • hello-interval: configure hello interval.
  • hold-time: configure hold time.
  • next-hop-self: configure EIGRP next-hop-self.
  • no: negate a command or set its defaults.
  • passive-interface: suppress address updates on an interface.
  • shutdown: disable Address-Family on interface.
  • split-horizon: perform split horizon.
  • summary-address: perform address summarization.

Per-AF-Topology Section

  • Relates to the support of multiple routing topologies in EIGRP.
  • Outside the scope of CCIE Routing and Switching certification.
  • A topology is defined as a subset of routers and links in a network for which a separate set of routes is calculated.
  • The base topology is the default routing environment that exists prior to enabling MTR.
  • Any additional topologies are known as class-specific topologies and are a subset of the base topology.
  • Each class-specific topology carries a class of traffic and is characterized by an independent set of Network Layer Reachability Information (NLRI) that is used to maintain separate routing tables and FIB databases.
  • The router can perform independent route calculation and forwarding for each topology.
  • Multiple topologies can be used to segregate traffic classes (for example, route data, voice, and video over different links).
  • MTR is not equivalent to VRF, because they share the common address space, and they are not intended to provide address conservation or reuse.
  • On routers without MTR support, only the topology base will be available.

Address Family Topology configuration commands:
  • auto-summary: enable automatic network number summarization.
  • default: set a command to its defaults.
  • default-information: control distribution of default information.
  • default-metric: set metric of redistributed routes.
  • distance: define an administrative distance.
  • distribute-list: filter entries in EIGRP updates.
  • eigrp: EIGRP specific commands.
  • exit-af-topology: exit from Address Family Topology configuration mode.
  • maximum-paths: forward packets over multiple paths.
  • metric: modify metrics and parameters for advertisement.
  • no: negate a command or set its defaults.
  • offset-list: add or subtract offset from EIGRP metrics.
  • redistribute: redistribute IPv4 routes from another routing protocol.
  • snmp: modify SNMP parameters.
  • summary-metric: specify summary to apply metric/filtering.
  • timers: adjust topology specific timers.
  • traffic-share: how to compute traffic share over alternate paths.
  • variance: control load balancing variance.

  • show commands have also been updated.
  • Instead of show ip eigrp ..., the new syntax show ip eigrp address-family ipv4 is used.
  • The older show commands are still acceptable for named mode.