Huge round trip time between a pair of routers

[v.nastase]

Hi

My company has a network comprised of 200 hundred routers connected through E1 lines. We are using OSPF as routing protocol with some defined OSPF areas.

In last week I have experienced an incident between two routers connecte through 1 E1 line. The controllers from both side are configured unframed and the associated serial interfaces are configured with PPP.

The problem encountered is even we don't have any type of errors on both sides or router low capacity (memory, processor) the round trip time between thsi two routers is about 300msec (huge).

Does anybody know what could generate this RTT (normal is 7 or 10 msec as the others lines) ?

Thanks in advance for your help

[lgijssel]

Hello,

Some tips to help with troubleshooting.

Is this a "true"point-point link between these two routers or do you have PPP-uplinks to a provider cloud? If it is point-point, which side generates the clock? Check the E1 controllers to see if they are not both set as clock source.

One should have:

controller E1 0/3

clock source internal

The other one should have no setting which equals the default: clock source line.

Please verify the path that your data takes with traceroute; is it really going from one router's interface to the other?

Then you may also check bandwidth parameter on the serials, should be: bandw 2048.

Regards,

Leo

[v.nastase]

Hi Leo

I checked everything you advice me, and all is OK.

Something else to verify?

Thanks

[smif101]

I would swap out the interface on each of them one at a time. Also can you post the show interface on both routers.

[v.nastase]

Core1#sh int ser1/0:1

Serial1/0:1 is up, line protocol is up

Hardware is DSCC4 Serial

Internet address is 10.15.254.9/30

MTU 1500 bytes, BW 2048 Kbit, DLY 20000 usec,

reliability 255/255, txload 8/255, rxload 1/255

Encapsulation PPP, loopback not set

Keepalive set (10 sec)

DTR is pulsed for 2887647 seconds on reset, Restart-Delay is 0 secs

LCP Open

Open: IPCP, CDPCP

Last input 00:00:02, output 00:00:02, output hang never

Last clearing of "show interface" counters 01:43:53

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 0/51/256 (active/max active/max total)

Reserved Conversations 0/0 (allocated/max allocated)

Available Bandwidth 1536 kilobits/sec

5 minute input rate 7000 bits/sec, 7 packets/sec

5 minute output rate 71000 bits/sec, 12 packets/sec

103504 packets input, 17972010 bytes, 0 no buffer

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

26 input errors, 7 CRC, 19 frame, 0 overrun, 0 ignored, 0 abort

139419 packets output, 65868771 bytes, 0 underruns

0 output errors, 0 collisions, 0 interface resets

0 output buffer failures, 0 output buffers swapped out

0 carrier transitions

Timeslot(s) Used: UNFRAMED, SCC: 0, Transmitter delay is 0 flags

Core2#sh int ser0/0:1

Serial0/0:1 is up, line protocol is up

Hardware is PowerQUICC Serial

Internet address is 10.15.254.10/30

MTU 1500 bytes, BW 2048 Kbit, DLY 20000 usec,

reliability 255/255, txload 2/255, rxload 5/255

Encapsulation PPP, loopback not set

Keepalive set (10 sec)

LCP Open

Open: IPCP, CDPCP

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

Last clearing of "show interface" counters 03:56:11

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 0/98/256 (active/max active/max total)

Reserved Conversations 0/0 (allocated/max allocated)

Available Bandwidth 1536 kilobits/sec

5 minute input rate 48000 bits/sec, 16 packets/sec

5 minute output rate 22000 bits/sec, 15 packets/sec

375536 packets input, 164911509 bytes, 0 no buffer

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

65 input errors, 28 CRC, 36 frame, 0 overrun, 0 ignored, 1 abort

284842 packets output, 52383534 bytes, 0 underruns

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