I'm trying to enable stac compression on an HDLC T1 between a 2621 and 6513. On the 2621 int s0/0 config I issue the "compress stac" command and on the 6513 s3/1/0/9:1 interface I issue the same. The link between the two devices stays up, meaning I can be in the 6513 and telnet to the other end of the link and login to the 2621. I can do a "sh compress" and see statistics incrementing for the compression but traffic flow just stops. Meaning end users at the 2621 site cannot ping upstream or browse the web. If I look at the "sh ip cache flow" stats on the 2621 the destination interface for all traffic is Null instead of S0/0.
When I turn compression off, everything is fine. Does the 2621 support software compression? Should I try a different encap such as ppp on the link? Is it necessary to reboot one or both devices once compression is enabled?
6513 IOS 12.2(18)SXF17a
2621 IOS 12.3(13)
This is strange... In any case, the 2621 should definitely support software compression (although it may increase its CPU load considerably). If possible, try using the PPP on the link. The PPP will, in addition to using the compression, actually negotiate whether is it possible to use a common compression algorithm.