Tag Archives: EIGRP

3.5 eigrp bw and dly table

dly and bw eigrp


the above is an excellent explanation of this tricky subject.


METRIC=256∗[( k1∗bandwidth) + (k3∗delay)]

or better yet


FastEthernet0/0 is up, line protocol is up
Hardware is AmdFE, address is cc01.0bb4.0000 (bia cc01.0bb4.0000)
Internet address is
MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,

R1#sh int lo0
Loopback0 is up, line protocol is up
Hardware is Loopback
Internet address is
MTU 1514 bytes, BW 8000000 Kbit, DLY 5000 usec,

R1#sh int s3/0
Serial3/0 is up, line protocol is up
Hardware is M4T
Internet address is
MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec,

and this excellent article from:




metric = 10^7 (10000000) divided by least bandwidth along the given path + cumulative delay along the path times 256

3.3.n Implement and troubleshoot routing protocol authentication

eigrp uses only md5 authentication, config below:

R1(config)#key chain CHAIN (go into key chain mod and define the key)
R1(config-keychain)#key 1 (give the key a numerical value)
R1(config-keychain-key)#key-string CHAINED (define key-string)
R1(config-keychain-key)#int f0/0 (go into interface)
R1(config-if)#ip authentication mode eigrp 100 md5 (set authentication mode to md5)
R1(config-if)#ip authentication key-chain eigrp 100 CHAIN (specify the key chain made in config mode, and repeat for neighbor)
R1#debug eigrp packet
EIGRP Packets debugging is on
*Mar  1 00:52:27.279: EIGRP: Sending HELLO on FastEthernet1/0
*Mar  1 00:52:27.279:   AS 100, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0
*Mar  1 00:52:27.363: EIGRP: received packet with MD5 authentication, key id = 1

this does not show up specifically in the blueprint but i’m adding it for completeness

3.5 EIGRP [for IPv4 and IPv6]

eigrp neighbor table


the H column records the order in which the neighbors were learned

address and interface columns record the ip address of the neighbor and the interface on which the neighbor’s Hello’s are received

the Hold time is the amount of time that a router will consider a neighbor alive without receiving  hello packets. The hold time is typically three times the hello interval. You can adjust the hold time with the ip hold-time eigrp command.

uptime the time since the neighbor was added to the table

SRTT (Smoothed Round-Trip Time) With EIGRP, a purposefully slowly changing measurement
of round-trip time between neighbors, from which the EIGRP RTO is calculated.

RTO (Retransmission Timeout) With EIGRP, a timer starts when a reliable (to be
acknowledged) message is transmitted. For any neighbor(s) failing to respond in its RTO, the
RTP protocol causes retransmission. RTO is calculated based on SRTT.

Q cnt(count) indicates the number of enqueued packets

Seq Num is the sequence number of the last update, query, or reply packet received from the neighbor