EIGRP Summary Route AD

TE,

I'm currently reading the ROUTE Foundation Learning Guide. I noticed early in the book (pg. 42) lists a table of administrative distances... nothing out of the ordinary but I noticed EIGRP's summary routes has an administrative distance of 5. I didn't recall ever seeing a 5 without it being manually configured. I checked Cisco's site and found this link. This table was the exact table that was from the book. I decided to lab a topology of three routers and I could not produce an administrative distance of 5 for summary routes without manually configuring it. Here's the code from the routers.

R1's info:

R1(config)#do sh run int s0/0  
Building configuration...

Current configuration : 68 bytes
!
interface Serial0/0
 ip address 192.168.13.1 255.255.255.248
end

R1(config)#do sh run int s0/1  
Building configuration...

Current configuration : 68 bytes
!
interface Serial0/1
 ip address 192.168.12.1 255.255.255.248
end

R1(config)#do sh ip route      
! removed for clarity

Gateway of last resort is not set

     192.168.12.0/29 is subnetted, 1 subnets
C       192.168.12.0 is directly connected, Serial0/1
     192.168.13.0/29 is subnetted, 1 subnets
C       192.168.13.0 is directly connected, Serial0/0
     2.0.0.0/22 is subnetted, 1 subnets
D       2.2.0.0 [90/2297856] via 192.168.12.2, 00:14:43, Serial0/1
     3.0.0.0/22 is subnetted, 1 subnets
D       3.3.0.0 [90/2297856] via 192.168.13.3, 00:01:42, Serial0/0
     192.168.23.0/29 is subnetted, 1 subnets
D       192.168.23.0 [90/2681856] via 192.168.13.3, 00:16:28, Serial0/0
                     [90/2681856] via 192.168.12.2, 00:16:28, Serial0/1

R1(config)#do sh run | s eigrp 
router eigrp 1
 network 192.168.12.0
 network 192.168.13.0
 no auto-summary
R1(config)#

R1 is showing routes 2.2.0.0 & 3.3.0.0 as an administrative distance of 90 (which is EIGRP internal route administrative distance).

R2's info:

R2#sh run int s0/0
Building configuration...

Current configuration : 120 bytes
!
interface Serial0/0
 ip address 192.168.23.2 255.255.255.248
 ip summary-address eigrp 1 2.2.0.0 255.255.252.0 5
end

R2#sh run int s0/1
Building configuration...

Current configuration : 120 bytes
!
interface Serial0/1
 ip address 192.168.12.2 255.255.255.248
 ip summary-address eigrp 1 2.2.0.0 255.255.252.0 5
end

R2#sh ip route
! removed for clarity

Gateway of last resort is not set

     192.168.12.0/29 is subnetted, 1 subnets
C       192.168.12.0 is directly connected, Serial0/1
     192.168.13.0/29 is subnetted, 1 subnets
D       192.168.13.0 [90/2681856] via 192.168.23.3, 00:05:05, Serial0/0
                     [90/2681856] via 192.168.12.1, 00:05:05, Serial0/1
     2.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
D       2.2.0.0/22 is a summary, 00:05:05, Null0
C       2.2.1.0/24 is directly connected, Loopback1
C       2.2.2.0/24 is directly connected, Loopback2
C       2.2.3.0/24 is directly connected, Loopback3
     3.0.0.0/22 is subnetted, 1 subnets
D       3.3.0.0 [90/2297856] via 192.168.23.3, 00:05:05, Serial0/0
     192.168.23.0/29 is subnetted, 1 subnets
C       192.168.23.0 is directly connected, Serial0/0

R2#sh run | s eigrp
 ip summary-address eigrp 1 2.2.0.0 255.255.252.0 5
 ip summary-address eigrp 1 2.2.0.0 255.255.252.0 5
router eigrp 1
 network 2.2.0.0 0.0.3.255
 network 192.168.12.0
 network 192.168.23.0
 no auto-summary
R2#

R3's info:

R3#sh run int s0/0
Building configuration...

Current configuration : 120 bytes
!
interface Serial0/0
 ip address 192.168.13.3 255.255.255.248
 ip summary-address eigrp 1 3.3.0.0 255.255.252.0 5
end

R3#sh run int s0/1
Building configuration...

Current configuration : 120 bytes
!
interface Serial0/1
 ip address 192.168.23.3 255.255.255.248
 ip summary-address eigrp 1 3.3.0.0 255.255.252.0 5
end

R3#sh ip route
! removed for clarity

Gateway of last resort is not set

     192.168.12.0/29 is subnetted, 1 subnets
D       192.168.12.0 [90/2681856] via 192.168.23.2, 00:23:53, Serial0/1
                     [90/2681856] via 192.168.13.1, 00:23:53, Serial0/0
     192.168.13.0/29 is subnetted, 1 subnets
C       192.168.13.0 is directly connected, Serial0/0
     2.0.0.0/22 is subnetted, 1 subnets
D       2.2.0.0 [90/2297856] via 192.168.23.2, 00:22:09, Serial0/1
     3.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
D       3.3.0.0/22 is a summary, 00:09:08, Null0
C       3.3.1.0/24 is directly connected, Loopback1
C       3.3.2.0/24 is directly connected, Loopback2
C       3.3.3.0/24 is directly connected, Loopback3
     192.168.23.0/29 is subnetted, 1 subnets
C       192.168.23.0 is directly connected, Serial0/1

R3#sh run | s eigrp
 ip summary-address eigrp 1 3.3.0.0 255.255.252.0 5
 ip summary-address eigrp 1 3.3.0.0 255.255.252.0 5
router eigrp 1
 network 3.3.0.0 0.0.3.255
 network 192.168.13.0
 network 192.168.23.0
 no auto-summary
R3#

Am I missing something? Thanks.

-Peanut

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Comments

kidfry

I'm in the process of reading this book as well - In fact, I just received it last week... Ironically, I'm just starting Chapt. 2 EIGRP as well!

Anyway... On pg. 113 within the highlighted 'Note' section, it states the following!

You will notice the EIGRP summary route with an AD of 5 only on the local router that is performing the summarization (with the ip summary-address eigrp command), by using the 'show ip route network' command, where network is the specified summarized route.

Does this help?

CCNAwannabe

It looks like the AD command is only in effect for the local routers summary address.. Check this out:

Cisco IOS IP Configuration Guide, Release 12.2 - Configuring EIGRP - Cisco Systems

Look under Configuring Floating Summary Routes

Quite interesting...

peanutnoggin

Kidfry,

You're spot on... Thanks for pointing that out in the book. After flipping to that page, I now understand. I labbed the configuration again and I was able to see the following:

R1#sh ip route 172.16.0.0 255.255.248.0
Routing entry for 172.16.0.0/21
  Known via "eigrp 10", [b]distance 5[/b], metric 128256, type internal
  Redistributing via eigrp 10
  Routing Descriptor Blocks:
  * directly connected, via Null0
      Route metric is 128256, traffic share count is 1
      Total delay is 5000 microseconds, minimum bandwidth is 10000000 Kbit
      Reliability 255/255, minimum MTU 1514 bytes
      Loading 1/255, Hops 0

CCNAWannabe, thank you too for the link.

-Peanut