Routing TCP/IP, Volume 1 (2nd Edition)

The EIGRP configurations are

RTA:

router eigrp 5 network 172.16.0.0 network 172.18.0.0

RTB:

router eigrp 5 network 172.16.0.0

RTC:

router eigrp 5 network 172.16.0.0 network 172.17.0.0

This solution uses a key chain named CCIE and key strings named exercise2a and exercise2b. Assuming today's date is November 30, 2004, and the first key begins being used at 8:30 AM, the configurations of the serial interfaces are

key chain CCIE key 1 key-string exercise2a accept-lifetime 08:30:00 Dec 2 2004 08:30:00 Jan 1 2005 send-lifetime 08:30:00 Dec 2 2004 08:30:00 Jan 1 2005 key 2 key-string exercise2b accept-lifetime 08:30:00 Jan 1 2005 infinite send-lifetime 08:30:00 Jan 1 2005 infinite ! interface Serial0 ip address 172.16.3.19X 255.255.255.252 ip authentication key-chain eigrp 5 CCIE ip authentication mode eigrp 5 md5

The EIGRP configuration of RTD is

router eigrp 5 network 172.16.0.0 network 172.17.0.0 no auto-summary

Auto-summarization must also be turned off on RTC.

The EIGRP configuration of RTF is

router eigrp 5 network 172.16.0.0 network 172.18.0.0 no auto-summary

The statement ip summary-address eigrp 5 172.18.10.192 255.255.255.224 is added to RTA's interface on subnet 172.18.10.96/27. Also, note that auto-summarization must be turned off on RTA, because of the appearance of the 172.16.0.0 network on RTF.

RTA can send a summary address of 172.16.3.128/25 to RTF and a summary address of 172.16.3.0/25 to RTB. All other summarization is performed automatically.