udld

[ciscoforum]

udld basic questions

1.what kind of hello packets UDLD is using? multicast?

2.only aggressive mode send hello packet? non-aggessive will detect link problem by real traffic?

Thanks

[pkhatri]

Answers to your questions:

1. UDLD sends packets to a destination MAC address of 0100.0CCC.CCCC, which is a multicast address. It uses the following format:

UDLD SNAP format:

LLC value 0xAAAA03

Org Id 0x00000C

HDLC protocol type 0x0111

2. Both aggressive and normal mode UDLD uses UDLD messages; the difference is that the normal mode UDLD will consider the port to be in a "undetermined" state if the hellos time out. In aggressive mode, the port will be disabled ..

Hope that helps - pls do rate the post if it does.

Paresh