EIGRP Named Mode – Configuration Tutorial

EIGRP Named Mode or Multi-AF Mode is a new development in EIGRP starting in Version 15.x

Its reason for being is to simplify the EIGRP configuration into one place, as previously with EIGRP classic version the configuration was between the interface and the global process which made it harder to see all the configuration relating to EIGRP together.

In the back end nothing has changed so you can run EIGRP between to neighbors with one running classic mode and the other running named mode without a problem.

Using the simple topololgy below we will explore the basic setup and also look at authentication and eigrp named mode redistribution configuration.

First lets configure basic connectivity between R1 & R2

R1 

int e0/0
ip address 10.0.21.1 255.255.255.252

int lo0
ip add 1.1.1.1 255.255.255.255

R2 

int e0/0
ip address 10.0.21.2 255.255.255.252

int lo0
ip add 2.2.2.2 255.255.255.255

Before configuring EIGRP verify connectivity between R1 & R2

R1#ping 10.0.21.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.0.21.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 120/148/176 ms

Now we have verified connectivity lets step right into EIGRP Named Mode configuration.
With EIGRP classic mode you typed router eigrp and then picked a number for the AS Number – with named mode you have two options and the second is a word.

Choose a word and hit enter, you then have to configure the address-family and autonomous-system number. The EIGRP name can be locally significant but the
AS number has to match between routers as in classic mode.

R1(config)#router eigrp ROGER
R1(config-router)#address-family ipv4 unicast autonomous-system 12

Now lets view the EIGRP named mode configuration

R1#sh run | sec router eigrp
router eigrp ROGER
!
address-family ipv4 unicast autonomous-system 12
!
topology base
exit-af-topology
exit-address-family
R1#

At this point no interfaces have been enabled for EIGRP so no neighbors are coming up. We need to go back into the named configuration and add a network statement.

R1(config)#router eigrp ROGER
R1(config-router)#address-family ipv4 unicast autonomous-system 12
R1(config-router-af)#network 10.0.21.1 0.0.0.0
R1(config-router-af)#network 1.1.1.1 0.0.0.0
R1(config-router-af)#end
*Feb  9 21:57:21.375: %DUAL-5-NBRCHANGE: EIGRP-IPv4 12:
Neighbor 10.0.21.2 (FastEthernet0/0) is up: new adjacency

I have already configured R2 so you can see the EIGRP neighbor comes up.

To verify connectivity to the loopback of R2 – lets ping 2.2.2.2

R1#ping 2.2.2.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2.2.2.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 92/125/156 ms

You may be wondering what is the difference between Named Mode and Multi-AF Mode – the short answer is nothing. They are the same thing, even though the CCIE V5 Blueprint lists them as two separate items to learn which does provide an element of confusion.

EIGRP Named Mode Redistribution

Now lets take a look at something which on the face of it looks quite simple but with eigrp named mode has become a bit more complicated and that is redistribution.

First lets expand our topology to include another router running OSPF.
R3 has its loopback 3.3.3.3 in OSPF and we will be redistributing OSPF into EIGRP on R2

The first question is where under the new EIGRP configuration do you do the redistribution? Lets find out.

Go into the eigrp named mode, specify the address family and it is under topology base

R2#conf t
Enter configuration commands, one per line. End with CNTL/Z.
R2(config)#router eigrp ROG
R2(config-router)#address-family ipv4 unicast autonomous-system 12
R2(config-router-af)#?
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 address advertisement
neighbor Specify an IPv4 neighbor router
network Enable routing on an IP network
no Negate a command or set its defaults
shutdown Shutdown address family
timers Adjust peering based timers
topology Topology configuration mode

R2(config-router-af)#topology base
R2(config-router-af-topology)#?
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
fast-reroute Configure Fast-Reroute
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

R2(config-router-af-topology)#redistribute ospf 1 metric 1 1 1 1 1

Remember when redistributing into EIGRP you have to specify a metric. I have just chosen all ones here but as you will see this is going to cause problems.

Lets see if we now have the prefix 3.3.3.3/32 in the routing table of R1

R1#sh ip route 3.3.3.3
% Network not in table
R1#

So why is that?

Lets look to see if the prefix is in the topology database

R1#sh ip eigrp topology 3.3.3.3/32
EIGRP-IPv4 VR(ROGER) Topology Entry for AS(12)/ID(1.1.1.1) for 3.3.3.3/32
State is Passive, Query origin flag is 1, 0 Successor(s), FD is Infinity, RIB is 4294967295
Descriptor Blocks:
10.0.21.2 (FastEthernet0/0), from 10.0.21.2, Send flag is 0x0
Composite metric is (655361310720/655360655360), route is External
Vector metric:
Minimum bandwidth is 1 Kbit
Total delay is 20000000 picoseconds
Reliability is 1/255
Load is 1/255
Minimum MTU is 1
Hop count is 1
Originating router is 2.2.2.2
External data:
AS number of route is 12
External protocol is OSPF, external metric is 2
Administrator tag is 0 (0x00000000)
EIGRP-IPv4 Topology Entry for AS(1)/ID(1.1.1.1)
%Entry 3.3.3.3/32 not in topology table
R1#

It is so why is not being installed into the routing table? Well with EIGRP named mode it uses a new feature called wide metrics, this is to overcome the limitations with the scaling of higher bandwidth links and to make the metrics more granular. However in our example our seed metric of 1 has caused an issue and if you look at the RIB metric above you will see it is 4294967295. The IOS RIB cannot only support a 32 bit number however the EIGRP wide metrics can now support a 64 bit number. The issue here is the Metric in the RIB is so high it cannot be installed into the routing table.

Lets change our seed metric to be a bit higher

R2(config-router-af-topology)#redistribute ospf 1 metric 10 10 255 1 1500

Checking on R1 again we can see this metric has now come within the limits and is installed into the routing table

R1#sh ip eigrp topology 3.3.3.3/32
EIGRP-IPv4 VR(ROGER) Topology Entry for AS(12)/ID(1.1.1.1) for 3.3.3.3/32
State is Passive, Query origin flag is 1, 1 Successor(s), FD is 65543208960, RIB is 512056320
Descriptor Blocks:
10.0.21.2 (FastEthernet0/0), from 10.0.21.2, Send flag is 0x0
Composite metric is (65543208960/65542553600), route is External

R1#sh ip route 3.3.3.3
Routing entry for 3.3.3.3/32
Known via "eigrp 12", distance 170, metric 512056320, type external
Redistributing via eigrp 12
Last update from 10.0.21.2 on FastEthernet0/0, 00:00:27 ago
Routing Descriptor Blocks:
* 10.0.21.2, from 10.0.21.2, 00:00:27 ago, via FastEthernet0/0
Route metric is 512056320, traffic share count is 1
Total delay is 110 microseconds, minimum bandwidth is 10 Kbit
Reliability 255/255, minimum MTU 1500 bytes
Loading 1/255, Hops 1

So when using EIGRP named mode you need to be careful of the higher metrics.

There is another feature in play and that is the metric rib-scale but default it is 128. This is a factor that EIGRP uses to scale down the metric and if we look at the example above you can see the composite metric is 65543208960 If we divide this by 128 you will get the metric used in the routing table.

65543208960/128=65543208960

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Roger Perkin - CCIE #50038 is a Network Automation Engineer & CCIE Consultant based in the UK, currently working for Softcat Plc as a Senior Network & Security Consultant.
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