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New Member

eigrp over Wan

Should EIGRP be used over a T1 serial link ?

EIGRP appears to be working fine, but can't explain an occasional/small amount of packet loss


Re: eigrp over Wan


There absolutely no inherent problem with running EIGRP over a T1 link. If you are observing packet loss, it could be one of the following reasons and that's where you should be concentrating:

- line errors leading to CRCs, slips which cause packet errors

- congestion on the link

The output of 'show interface' should help you to identify where the problem lies.

Pls do remember to rate posts.


New Member

Re: eigrp over Wan

Thanks for the reply.

What is a "normal" number of interface errors ?

see output below, which has built over about 3 days.

There is clearly some packet loss, but not much...

When I continuous ping to yahoo/google across this link, I lose ping packets.

Router2#show interfaces serial 1x

Serial 1x is up, line protocol is up

Hardware is cyBus T3

Description: x

Internet address is x

MTU 1500 bytes, BW 1536 Kbit, DLY 20000 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation HDLC, crc 16, loopback not set

Keepalive set (10 sec)

Last input 00:00:00, output 00:00:03, output hang never

Last clearing of "show interface" counters 3d20h

Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0

Queueing strategy: weighted fair

Output queue: 0/1000/64/0 (size/max total/threshold/drops)

Conversations 0/102/256 (active/max active/max total)

Reserved Conversations 0/0 (allocated/max allocated)

Available Bandwidth 1152 kilobits/sec

5 minute input rate 1000 bits/sec, 1 packets/sec

5 minute output rate 0 bits/sec, 0 packets/sec

703643 packets input, 98689312 bytes, 0 no buffer

Received 0 broadcasts, 0 runts, 0 giants, 0 throttles

42 input errors, 0 CRC, 42 frame, 0 overrun, 0 ignored, 2 abort

212968 packets output, 17740211 bytes, 0 underruns

0 output errors, 0 collisions, 2 interface resets

0 output buffer failures, 0 output buffers swapped out

4 carrier transitions no alarm present

Timeslot(s) Used: 1-24, Transmitter delay is 0 flags, transmit queue length 5


Re: eigrp over Wan


On the face of it, the error count does seem very small so I'm not sure if there really is an issue with the line as such.

To troubleshoot this further, I suggest that you do a continuous ping to the WAN IP address at the other side of this link.

Then, do the same to yahoo/google.

If you find that you don't get packet loss when pinging the WAN IP but do get packet loss when pinging internet addresses, then the problem is further downstream and you need to get your ISP to investigate the issue. But if you don't get 100% ping responses back when pinging the WAN address, your line must have issues.

Pls do remember to rate posts that help.


New Member

Re: eigrp over Wan

Do you have any time of traffic shaping mechanism, in your network;this can definetly cause these problems you are experiencing, also check the limi line status.

If that works ok; then it could be possibly a mtu mismatch error. HTH

New Member

Re: eigrp over Wan


U have to check it at physical layer also that the both side router is connected to earthing.

plz see the sh int se x.x:x for both side. it may be that one side u get very low CRC but on other side u get more CRc errors

Pls do remember to rate posts