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Community Member

Routing Table

Hi,in my router there is 64F/256D, In this memory configuration how big routing table can be operate by the Router? How do I know that Memory is getting full to operate full routing table.

7 REPLIES
Hall of Fame Super Gold

Re: Routing Table

Which router is that first of all? And why do you think you need full routing ?

Cisco Employee

Re: Routing Table

Hello,

Most certainly, 256 MB of RAM is absolutely insufficient to hold the full routing table. These data are taken out from the route-views project router:

From the show ip route summary:

Route Source Networks Subnets Overhead Memory (bytes)

Total 145651 169353 19855808 53208068

The routing table alone consumes about 512 MB RAM.

From the show ip bgp summary:

BGP using 806689552 total bytes of memory

BGP is using another 800 MB of memory.

So for a full routing table, your router must have at least 2GB of RAM, and if you turned on the IP CEF, internal routing protocols and various other services, the memory consumption would only increase further. That being said, Paolo is right: are you sure you need the full routing table?

Best regards,

Peter

Community Member

Re: Routing Table

I dont need full routing table, actually I need to confirm that how much memory is presetnly consumed by the routing table. Then I can calculate rest of the Memory.

Cisco Employee

Re: Routing Table

Hello,

Try using the command show ip route summary. That output will give information about the memory usage of your current routing table.

Note, however, that if you are using CEF (which you probable are) then the routing table is inserted into the CEF tree. Also, the adjacency table that the CEF points into consumes memory. These data structures will further allocate more memory. Unfortunately, I don't know the command to find out the memory allocated by the CEF and adjacency tables. Anyone to help here?

Best regards,

Peter

Hall of Fame Super Bronze

Re: Routing Table

From the show ip route summary:

Route Source Networks Subnets Overhead Memory (bytes)

Total 145651 169353 19855808 53208068

The routing table alone consumes about 512 MB RAM.

Peter,

How you came out to that conclusion wrt 512MB RAM?

Based on the numbers above - total memory + overhead amounts to 73,063,876 bytes (73 MB)

Cisco Employee

Re: Routing Table

Edison,

I must have been blind or something! You are absolutely correct. That routing table consumes about 73 MB, exactly as you indicated. Phew, I really screwed this one...

Thank you for correcting me!

Best regards,

Peter

Hall of Fame Super Bronze

Re: Routing Table

Peter,

You've been on target 99.999% of the time. It shows you are human :)

Thanks for joining us on these forums.

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