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IP CEF per-destination load balance

Hi,

I found in cisco documentation that per destination load balancing is the default configuration of CEF. My question is, does FIB table next-hop (adjacency) change? Let's say, if my router has two links (Serial 0 and Serial 1) to destination network B. CEF points the FTP traffic to Serial 0 and Once Network A stops sending traffic. does FIB flush it's table? Let's say the same FTP traffic to the same source and destination (Network A to Network B) will the traffic have a chance to route the traffic to Serial1?

Network A ------Router--------Serial 0 ----------------Network B

                               |                                      |

                               |                                      |

                               ---------Serial 1-------------------|

http://www.cisco.com/en/US/docs/ios/12_1/switch/configuration/guide/xcdcefc.html#wp1000956


Thanks in advance

4 REPLIES

Re: IP CEF per-destination load balance

Hi,

1) does FIB flush it's table?

No, it doesn't.

2) Let's say the same FTP traffic to the same source and destination (Network A to Network B) will the traffic have a chance to route the traffic to Serial1?

No, "for load balancing on IP address basis a hashcode is generated out of the addresses. ... For any given pair of source and destination addresses the hashcode is always the same, thus guaranteeing that always the same path is used."

See

http://www.cisco.com/en/US/customer/products/hw/modules/ps2033/prod_technical_reference09186a00800afeb7.html#wp16240

for details.

HTH,

Milan

Community Member

Re: IP CEF per-destination load balance

Hi milan.kulik,

Thank you for the response. I tried going to the link you provided but my access doesn't allow me to view the link.

Appreciate your reply.

Re: IP CEF per-destination load balance

Hi,

this .pdf version of the document should be available to public:

http://www.cisco.com/warp/public/cc/pd/ifaa/pa/much/prodlit/loadb_an.pdf

BR,

Milan

Community Member

Re: IP CEF per-destination load balance

Hi Milan,

Once again. Thank you.

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