Cisco – Stacking Cisco Catalyst 3850 via Fibre

Fixed! Turns out, after slagging off the netgear, it was the cisco that was causing the problem. Seems when I configured the interface switchport access vlan 20 it didn't create vlan 20 on the switch automatically like it would normally.

Found it by doing a sh trunkand VLAN 20 wasn't included in any of the trunks, did a sh vlan and it wasn't listed either, so created it and all working. Very odd.

You have an elegant physical setup, but logically, it’s deficient in a lot of ways. You’re relying on layer 2 for all of your connections, which doesn’t provide any real failover your setup should provide. Luckily, you aren’t wasting any bandwidth with STP because you don’t have any redundant links; VLAN 100 and VLAN 200 only have a single way out, if I’m reading this correctly.

I can't implement multiple area OSPF because the CPE public subnets are too difficult to summarize and the public range is split over several POPs without hierarchy, so this would be inefficient.

I don’t even think you need to go as far as setting up multiple areas, the segment your concerned with is fairly small. Cisco recommends you stay under 50 routers per area, though, most will agree that you can exceed that amount by quite a significant margin and still be considered healthy. I have about 80 routers per area with no issues; Ron has even more than that without any hiccups.

• Implementation of EtherChannel between the access switches and CMTS.

This all hinges off what happens higher up in your network. If you’re significantly oversubscribing your distribution to core links, then you may not see any real benefit in increasing your bandwidth at the access layer. The same holds true if you’re doing this with your access to distribution.

Again, as most have mentioned in the comments, implementing OSPF would be pretty easy. If you were utilizing a layer 3 protocol, you would share that load across equal/unequal cost links, too. Perhaps a redundant link between your distribution switches would allow each access switch a redundant path out. As it stands, if one of your access links goes down, you lose an entire subnet (VLAN 100 or VLAN 200).