I have an office downstairs which requires approximately 500 feet of cat-5 to reach. We have a basic L2 switch in a closet at the halfway point which acts as a signal booster, and allows us to give connectivity to the downstairs office. This all worked fine until I wanted to use two runs instead of one, in order to give extra bandwidth and fault-tolerance to the connection. I was told on the Cisco Support forums that I could still use the same basic L2 switch at the halfway point if I use EtherChannel, and everything would work. This doesn't make sense to me... how could you avoid the network loop there? I've tried it, and sure enough, I get colliding packets due to the network loop it creates. STP kicks in and tries to correct it, but it doesn't seem to work, and all I get is chaos.
OK, so I was really skeptical that having a plain old L2 switch at the halfway point would work, and indeed, it seems this is the case. Is there a way to do this? Or perhaps this should work, but I've misconfigured something?
To me, it seems more logical to have another L3 switch to match the two I have on the endpoints, and configure it with two sets of EtherChannels, each of which connects to one of the other endpoint pairs.
Anyway, the question is, can I do EtherChannel over two hops, and if so, how? I'd just experiment, but its a pain to coordinate with building management to open up that closet, so I'd like to know what I'm doing beforehand.
Here's my config and other info:
(2x) Cisco sg300 switches (in L3 mode), one at each endpoint
(1x) Cheapo L2 smart switch, hereafter referred to as "the booster switch"
I'm using PaGP on the endpoints, not LACP
(2x) CAT-5 runs of less than 300' go from one endpoint to two of the ports on the booster switch, and then (2x) more runs of less than 300' go from two more ports of the booster switch to the other endpoint.
Cisco config here (private and unneeded details removed):
sw-sg300-10-454#show running-config config-file-header sw-sg300-10-454 v1.2.7.76 / R750_NIK_1_2_584_002 CLI v1.0 file SSD indicator encrypted @ ! no cdp run vlan database vlan 2-4 exit port-channel load-balance src-dst-mac-ip hostname sw-sg300-10-454 ! interface vlan 1 ip address 192.168.5.23 255.255.255.0 no ip address dhcp ! interface vlan 2 name data ! interface vlan 3 name voice ! interface vlan 4 name wireless ! interface gigabitethernet1 switchport trunk allowed vlan add 4 switchport trunk native vlan 2 ! interface gigabitethernet2 switchport trunk allowed vlan add 4 switchport trunk native vlan 2 ! interface gigabitethernet3 switchport trunk allowed vlan add 4 switchport trunk native vlan 2 ! interface gigabitethernet4 switchport trunk allowed vlan add 4 switchport trunk native vlan 2 ! interface gigabitethernet5 switchport trunk allowed vlan add 4 switchport trunk native vlan 2 ! interface gigabitethernet6 switchport trunk allowed vlan add 4 switchport trunk native vlan 2 ! interface gigabitethernet7 channel-group 1 mode on ! interface gigabitethernet8 channel-group 1 mode on ! interface Port-channel1 description to_other_endpoint switchport trunk allowed vlan add 2-4 ! sw-sg300-10-454#
Thanks for any pointers.
