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This is 3rd part from the EIGRP summariztion thread. Please read the previous two as well. I would like to test EIGRP stub feature to see what is the impact on EIGRP behavior. Ever network behind R4, R5 and R6 we may consider as a stub network. If we lose access to one of them, there is no need to query other routers as any of them is a transit network. I modify the configuration on R4-R6 routers: R4#sh run | s eigrp router eigrp TEST1 ! address-family ipv4 unicast autonomous-system 100 ! topology base exit-af-topology network 10.2.0.0 0.0.0.255 network 10.2.1.0 0.0.0.255 network 10.2.2.0 0.0.0.255 network 10.2.3.0 0.0.0.255 network 10.2.4.0 0.0.0.255 network 10.2.5.0 0.0.0.255 eigrp stub connected summary exit-address-family R4#     Now it’s time to shutdown a loopback5 (network 10.3.5.0/24) and check what we see on R4:     *Jul 21 18:26:47.874: EIGRP: Received UPDATE on Fa0/0 - paklen 44 nbr 10.2.0.2 *Jul 21 18:26:47.874: AS 100, Flags 0x0:(NULL), Seq 40

This is the 2nd part of the EIGRP summarization series. Please read previous post if you didn't to understand the topic better. The network diagram from previous post:       Below you can see routing tables from R4, R5 and R6 before summarization: R4#sh ip route Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP  D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area  N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2  E1 - OSPF external type 1, E2 - OSPF external type 2  i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2  ia - IS-IS inter area, * - candidate default, U - per-user static route  o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP  + - replicated route, % - next hop override Gateway of last resort is not set 10.0.0.0/8 is variably subnetted, 25 subnets, 2 masks D 10.0.0.0/24 [90/153600] via 10.2.0.2, 01:30:40, FastEthernet0/0 D 10.1.0.0/24 [90/204800] via 10.2.0.

Today I would like to play with EIGRP, check its recommended designs, settings, etc. Below you can see a diagram: I have a standard configuration (named version) on all of them: router eigrp TEST1 ! address-family ipv4 unicast autonomous-system 100 ! topology base exit-af-topology network 10.1.0.0 0.0.0.255 network 10.0.0.0 0.0.0.255   There are three topics I plan to go through in this and 2 next posts: 1) link failures without summarization 2) link failures with summarization 3) link failures with an EIGRP stub routing feature Let's start from the basic principals and then we move on. In stable network we should see 'hello' packets sent every 5 seconds: R1#debug eigrp packets all (UPDATE, REQUEST, QUERY, REPLY, HELLO, UNKNOWN, PROBE, ACK, STUB, SIAQUERY, SIAREPLY) EIGRP Packet debugging is on R1# *Jul 20 22:54:20.426: EIGRP: Sending HELLO on Fa0/0 - paklen 20 *Jul 20 22:54:20.426: AS 100, Flags 0x0:(NULL), Seq 0/0 interfaceQ 0/0 iidbQ un/rely 0