ANW2 OSPF REDLAN Gotcha

Ran into an interesting little issue with an ANW2 integration.  I’ve looked into it, and when you are using OSPF with ANW2 you don’t HAVE to use a REDLAN connection.  Normally, using the REDLAN is how you manually add external (static) routes to your ANW2 network (which normally you just configure as 0.0.0.0/0).  Turning on OSPF turns your radios into routers “speaking” OSPF, so when you connect your radio to an OSPF enabled router, the ANW2 radio network can receive external routes without needing to use a REDLAN connection.  I normally like to use a REDLAN connection because it provides a graphic depiction of an external connection to allow the radio Marines to more easily visualize how the radios are connecting to the larger network, but I have seen an un-intended consequence recently.

As I was working through the crawl, walk, run stages of ANW2 configuration, we started with two radios with a laptop connected to each radio.  We pinged between the radios and computers and the magic was happening.  When we moved into the walk stage, we configured a REDLAN connection, configured it with a quad zero, and showed the Marines how you can route to the external network, and back to the ANW2 network after configuring some static routes.  We then decided to work on the run stage (turn on OSPF).  The problem was, we never turned off the static 0.0.0.0/0 that we put into the REDLAN connection during the walk stage.  When we turned on OSPF, it took the network down because the 0.0.0.0/0 from the REDLAN connection (which had an administrative distance of 110) took precedence over our WAN connection, which received the default route via external EIGRP (administrative distance of 170).  I was initially confused by what the problem was, but when I started troubleshooting and noticed the default route for our POP router was via OSPF, I knew we had a problem.  Preferably, you would just remove your REDLAN static routes, but another option would be to change the administrative distance of either OSPF external routes, or EIGRP external routes.  At the time, it was much easier to make a change on a router instead of re-doing a CPA configuration file, so I just changed external OSPF to an administrative distance of 201.

This just goes to show that stale configs, even in radios, can come back to haunt you.

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