HEC Errors and Payload Scrambling

[briedcan]

Yesterday I deployed a 2620xm to a remote location. It connects back to our ABRs through a T1 that runs to an MGX. Layer one connectivity is good. I could run clean to a testset right in front of the ABRs. When everything is normaled up there are no conversations between the ABR and my 2620 and the MGX is seeing HEC errors.

This morning I found out the ABR (7500) is configured for payload scrambling. I did NOT configure the 2620xm for payload scrambling. Is payload scrambling enabled on the 2620 by default (I'm doubting it is)? Also, do you feel that when I turn on payload scrambling the HEC errors will clear and connectivity will be restored? Thanks for the help guys!

bc

[gmarogi]

Since both HEC generation/verification and cell scrambling are part of the Transmission Convergence (TC) Sublayer of the ATM physical layer, I think HEC errors will stop once both ends have been enabled or disabled for scrambling. The command reference says that scrambling is on by default for E1, but not for T1. So I am not sure how you are able to see scrambling enabled on 2600 without any configuration. There is more information available here :

http://www.cisco.com/en/US/tech/tk39/tk49/technologies_tech_note09186a00800d73b7.shtml

[briedcan]

Thanks for the doco! It really laid it out. I did find out that my problem was not due to payload scrambling though. The payload scrambling only effects the higher speed links (DS3 ^). My error was a little more elementary for some reason when I cut and pasted from word it changed the format of my pvc. When I took out the pvc and re-entered it everything came up fine. Regardless this forum is awesome for learning some of the tricks of the trade!

bc

[ddecan]

payload scrambling will effect your atm header, so the HEC will run errors.