RIP Routing

I did the INE v5 RIP section of the workbook.  The majority of the RIP configuration wasn't too bad.  There wasn't a triggered-update command section but that's cool.  Triggered updates aren't that bad and typically used for WANs anyways.  I can see it being used at a DMVPN spoke with "low" bandwidth, so that is something to keep in mind.  Well on to the other stuff I forgot and learned and found interesting.

One thing I forgot was that when using distribute-lists to filter traffic from gateways, it is better to use the /32 notation on the end of the gateway in the prefix-list.  I also wasn't thinking when it came to filtering all routes from a particular gateway that it is better to have a permit all prefix-list as well as the gateway.  The commands look like the following for matching any route that comes in any interface and deny it if it comes from the specific source.

ip prefix-list NOT_FROM_R4 deny 155.1.0.4/32
ip prefix-list NOT_FROM_R4 permit 0.0.0.0/0 le 32
!
ip prefix-list PERMIT_ALL permit 0.0.0.0/0 le 32
!
router rip
distribute-list prefix PERMIT_ALL gateway NOT_FROM_R4 in

I also forgot that there are changes within RIP that don't happen auto-magically.  You have to have patience and let the timers flush the routes out from the table.  Keep running show ip route and watch the timers.  If they go above the advertise timer, then the route is probably not being received any more and once it hits the invalid timer, it will hang out until it is flushed.  Patience, young grasshopper.

I always seem to get it wrong with extended ACLs being used to filter routes.  I knew that one some, the source meant one thing and the destination something else and then on other route types, it all meant something different.  INE explained this a little better so I just have to keep it in that rock that I call a head.  For BGP, the source field is the network address and the destination field is the subnet mask.  For IGPs, the source field is the update source (get it; source is the source) and the destination is the network address.  Now I just have to remember.

Ran into a another gotcha with RIP and default routing.  Completely wasn't thinking about it and forgot that RIP doesn't install a discard route on the originating router when it originates a default route.  It is added to the RIP database so that is cool.

Had a brain fart when it came to reliable default route origination.  Knew that it took IP SLA and a route map.  I was having issue with the middle piece because I am so used to it being that static routes are bad and should not be used on any of the labs.  Add a static route to a BOGON and use trac with that.

Learned something interesting from this all too.  I did not know that when you use ip unnumbered on an interface, RIP will no longer do validation source checking for RIP  updates coming into that interface.  Good information to know.

Well now that RIP is done, on to EIGRP.