Hi, I'm in last Computer engieneering Semester, Now i'm working on a educational institution for my practices, I've never practically used switches, now i'm working with cisco switches, the last days we were trying to re-configure the switches architecture, we tried to connect a catalyst 3560G with a 3550 (with SFP), apparently it went smoothly, The SFP interface LED goes green and "show interfaces GigabitEthernet 0/28" (28 is the port connected to the 3560) shows that link is up without any problems.
The problem is that both interfaces in both switches are removed from its respective VLANs, they dissapear when i issue the "show vlan" command, the just don't show up at all, so the other interfaces in VLAN can't see them. So my question is, what may be causing this behaviour? I tried to connect to another SFP with the same exact result. The weird part is that the 3560G was already connected to a 2950 without any problems at all!. Any ideas?
Thank you a lot in advance!
That is because the link is probably a trunk link now if you look at it and that is normal behavior , it will not show under the show vlan command if the link is a trunk and not an access port. Verify with a show interface trunk command.