EIGRP summarization

[yaroneis]

Can EIGRP auto-summary work in conjunction with 'ip summary-address eigrp' command or should the auto-summary be disabled first?

If they can, what can be the consequences that have to be taken into consideration?

Thanks in advance.

[ankurbhasin]

Hi Yaroneis,

I will recommend if you want to have subnet level of summarization then disable "auto summary" and then configure 'ip summary-address eigrp' because auto summary will summarize to network level and auto summary always supersedes the manual summary routes.

Also when you configure summarization remember to check for null route to prevent routing loop.

In new IOS codes static routes pointing to null interfaces are automatically generated for summary routes but still check it and if it is not available create one static route pointing to null interface.

Also for summary routes EIGRP assigne dthe admin distance as 5.

HTH

Ankur

[ruwhite]

Yes, you can run auto-summary with manuall summarization--the two will not interfere with each other. Normally, we tell people to turn auto-summarization off, but if your network is really designed with multiple class b's or class a's so that auto-summarization really works, then feel free to use it. Most of the time, auto-summarization doesn't catch externals (routes redistributed into EIGRP), so we would normally see auto-summarization used for the internal routes (when we see auto-summarization used at all), and manual summarization used for external routes.

HTH.

🙂

Russ.W