7750 trunk to Catalyst 2960

[rambo888888]

anyone have any idea to configure trunk between 7750 to cat 2960?

is it i only need to configure port trunk on 7750  and trunk on cat 2960?

what about hybrid port?

[Fred_Mancen_1]

Yes, both vendors use the 802.1Q as the standard protocol in trunk mode. Some years ago Cisco also used the ISL (a proprietary protocol), but nowadays it uses the 802.1Q. All you need to do is ensure that these parameters are correctly configured on both sides (note that I am mentioning the 3Com parameters with equivalent Cisco command beside):

port link-type trunk => switchport mode trunk

port trunk permit vlan <permitted_vlan_id_list> => switchport trunk allowed vlan <permitted_vlan_id_list>

port trunk pvid vlan <vlan_id> => switchport trunk native vlan <vlan_id>

3com uses 802.1Q as the standard => switchport trunk encapsulation dot1q

The hybrid port is cool, but the trunk is more recommended in this case, because it's easier to maintain and change the settings when needed than hybrid mode. The hybrid port permit that you assign more than one VLAN ID untagged on the connection, the trunk mode permit that you use just one VLAN ID untagged (PVID). The hybrid port is applicable when connecting devices that don't supports 802.1Q.

HTH

[rambo888888]

i already configured on cisco:

switchport mode trunk

switchport trunk allowed VLAN 205,209,50,51

on 3Com:

interface GigabitEthernet4/0/14


 port link-type trunk


 port trunk permit vlan all

suddenly i error log in CIsco switch:BPDU error

then the suddenly the interface VLAN 205 in 3com suddenly down.

is it i must put this command?

port trunk pvid vlan <vlan_id> => switchport trunk native vlan <vlan_id>

[Fred_Mancen_1]

Yes, you have to specify what is the native VLAN (PVID) of the trunk. This is the VLAN in which the BPDU traffic will pass.

It must be the same VLAN on both sides.

Regards

[rambo888888]

i follow your steps and both switches can work together now. but, the old vlan still cannot work with this configuration. i dont know how the previous engineer configure the old VLAN