Cisco – OSPF configuration in MESH topology

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).

To answer your question directly, this is expected behavior by OSPF and not a bug in Quagga.

So first, let's take a look at the DR/BDR section of the RFC.

Designated Router
    The Designated Router selected for the attached network.  The
    Designated Router is selected on all broadcast and NBMA networks
    by the Hello Protocol.  Two pieces of identification are kept
    for the Designated Router: its Router ID and its IP interface
    address on the network.  The Designated Router advertises link
    state for the network; this network-LSA is labelled with the
    Designated Router's IP address.  The Designated Router is
    initialized to 0.0.0.0, which indicates the lack of a Designated
    Router.

Backup Designated Router
    The Backup Designated Router is also selected on all broadcast
    and NBMA networks by the Hello Protocol.  All routers on the
    attached network become adjacent to both the Designated Router
    and the Backup Designated Router.  The Backup Designated Router
    becomes Designated Router when the current Designated Router
    fails.  The Backup Designated Router is initialized to 0.0.0.0,
    indicating the lack of a Backup Designated Router.

If the BDR field in the Hello packet header is set to 0.0.0.0, it means you do not have a BDR elected.

In your case this is because you have your other router set to a priority of 0, this makes the router ineligible to become a BDR (this is why you see "DROther" and not "BDR"). You just need to set the priority on your other router to something that isn't 0.

Here is the other piece from the RFC for some more context.

Router Priority
    An 8-bit unsigned integer.  When two routers attached to a
    network both attempt to become Designated Router, the one with
    the highest Router Priority takes precedence.  A router whose
    Router Priority is set to 0 is ineligible to become Designated
    Router on the attached network.  Advertised in Hello packets
    sent out this interface.

https://www.ietf.org/rfc/rfc2328.txt