Dell Force10 S4820T S4820T Configuration Guide - Page 232

www.dell.com | support.dell.com Use the following commands in the CONFIGURATION ROUTER BGP mode to configure BGP confederations. Command Syntax bgp confederation identifier as-number bgp confederation peers as-number [... as-number] Command Mode Purpose CONFIG-ROUTERBGP Specifies the confederation ID. AS-number: 0-65535 (2-Byte) or 1-4294967295 (4-Byte) CONFIG-ROUTERBGP Specifies which confederation sub-AS are peers. AS-number: 0-65535 (2-Byte) or 1-4294967295 (4-Byte) All Confederation routers must be either 4-Byte or 2-Byte. You cannot have a mix of router ASN support, Use the show config command in the CONFIGURATION ROUTER BGP mode to view the configuration. Enable route flap dampening When EBGP routes become unavailable, they "flap" and the router issues both WITHDRAWN and UPDATE notices. A flap is when a route • is withdrawn • is readvertised after being withdrawn • has an attribute change The constant router reaction to the WITHDRAWN and UPDATE notices causes instability in the BGP process. To minimize this instability, you may configure penalties, a numeric value, for routes that flap. When that penalty value reaches a configured limit, the route is not advertised, even if the route is up. In FTOS, that penalty value is 1024. As time passes and the route does not flap, the penalty value decrements or is decayed. However, if the route flaps again, it is assigned another penalty. The penalty value is cumulative and penalty is added under following cases: • Withdraw • Readvertise • Attribute change When dampening is applied to a route, its path is described by one of the following terms: • history entry-an entry that stores information on a downed route • dampened path-a path that is no longer advertised • penalized path-a path that is assigned a penalty The CLI example below shows configuring values to start reusing or restarting a route, as well as their default values. 232 | Border Gateway Protocol IPv4 (BGPv4)