Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 
Community Member

Serial2 is up, line protocol is down

I have a point to point t1 between a 3810 router and 7206 router. The 3810 is using the T1 controler port and s2. The 7206 is using T1 4/3 and serial s4/3:0 for the connection. I am using HDLC. If I loop either controller, the opposite serial interface will see the loop and go up, up. When I connect them together they both go UP, DOWN. They are set up with ESF/B8ZS. There is an IP address set up on the serial interface. Why am I seeing the Line Protocol down on the serail interface?


Re: Serial2 is up, line protocol is down

The line protocol down is due to a keepalive

failure; both sides are sending keepalives, but

they are being received in error. You should

try loopback tests starting local and moving

out towards the remote end, to verify the

integrity of the entire path.

As a test you can try disabling keepalives; the

line protocol will then go UP, but if there is

a problem with the line then your data will be

as effected as the keepalives were.

You might also want to ensure that both ends

have recent code; there may be issues with the

3810. In fact another test might be to

try another platform besides the 3810, just to

confirm it is not platform dependent.

CreatePlease to create content