Today i was playing with some eigrp summary route scenarios and one thing got me laughing. You know that summary routes in eigrp have a distance of 5 so when you set up a summary route, it installs a route for the whole summary to null0.
So I tried increasing the distance to 111 for the summary route so that I can send to this router a summary from some other router in e.g. ospf which has 110 as its distance.
I remembered that the option to change the distance of the summary was there somewhere…but it’s not there anymore. Only the leak-map option is left.
R5(config-subif)#ip summary-address eigrp 100 126.96.36.199 255.255.254.0 ?
leak-map Allow dynamic prefixes based on the leak-map
but what if we do it anyway?
R5(config-subif)#ip summary-address eigrp 100 188.8.131.52 255.255.254.0 20
%EIGRP: summary-address accepted but distance option deprecated; use summary-metric command for distance.
ROFL. Why would they deprecate this in favour of ”summary-metric”? This so doesn’t make sense…
Anyways, this also proves true in other cases so if you know a command should (once was?) there, try to use it anyway but be careful when upgrading ios because deprecated means it might be gone in the next release and you will be in trouble when you upgrade and cause an outage because of this 😉
In this case IOS was nice and converted the deprecated command automatically to:
summary-metric 184.108.40.206/23 distance 20
btw if you don’t want to install a route to null0, use distance 255:
summary-metric 220.127.116.11/23 distance 255
Note that in some ios versions doing this prevents the summary from being sent out AND it prevents more specific routes from being sent out either. So it’s like a distribute list with a < deny all routes from this router>. Of course, routes from other routers are still forwarded.