Flapping int. issue

[mlomairy]

How would you solve a flapping problem on a serial interface?

Regards

 

[mtashiro]

Depends what the problems is. It could be a faulty cable, issues with the carrier, configured incorrectly or a carrier issue.

Has the link been working? If so it is probably not a config issue.

Change the cabling, this is easy and inexpensive.

Have the carrier test the line.

 

[jamin123]

Try changing to a Loopback instead of IP address.

 

[mlomairy]

I'm connecting two routers 2520, 2610 back to back with a serial cable DB-60 to smart interface. The link keeps going up and down.
I've changed the cable, however, the interface still flaps.
from my point of view everything is fine, I just still have this annoying problem! below is the interfaces configurations:

Router 2520:
interface Serial0
ip address 10.1.1.1 255.255.255.0
no ip mroute-cache

Router 2610:
interface Serial0/1
ip address 10.1.1.2 255.255.255.0
no ip directed-broadcast
clockrate 64000

Any help will be highly appreciated.

 

[jamin123]

Are you using OSPF? If so choose a flat and quiet surface for your lab routers.

 

[mtashiro]

Under each interface change encapsulation to PPP instead of HDLC. Back to back connections work better with PPP.

Example:
interface serial0
encap ppp

 

[mlomairy]

Still having some problems with the interface going up and down, sometime when i clear all configuration, the physical interfaces get up but the serial protocol remain down! this is getting me crazy! everything seems to be correct, why it's not working?

please help.

 

[mtashiro]

is it a WIC-1DSUT1 card or a serial card? If it is a WIC-1DSU-T1 card test the card by putting a loopback plug in it, and test. Should stay up and you should be able to ping the interface.

If it does stay up the card is fine so call the carrier and have them test. You may want to have them test the line anyway.

 

[mlomairy]

I'm connecting the two routers back to back, one router with a serial interface and the other one with DB-60, the cables are fine as I've tested it before. I tried HDLC, and PPP, but still have the same problem, it's a basic lab that connect two routers through serial back to back setup.

 

[mtashiro]

Can you post the configs? Make sure the DCE side sets the clockrate and make sure that the side that sets the clockrate has the DCE side cable attached.

 

[fmonteiro]

It could also be a interface physical problem. On the 2520 change the serial interface from 0 to 1 and try again. If the problem persists change the serial interface on the 2610 side.