Dell PowerSwitch S4820T 9.50.1 Configuration Guide for the S4820T System - Page 193
Ignore Router-ID for Some Best-Path Calculations, Four-Byte AS Numbers, Command Settings
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internal configured, BGP advertises the metric configured in the redistribute command as MED. • If BGP peer outbound route-map has metric configured, all other metrics are overwritten by this configuration. NOTE: When redistributing static, connected, or OSPF routes, there is no metric option. Simply assign the appropriate route-map to the redistributed route. The following table lists some examples of these rules. Table 8. Redistributed Route Rules Command Settings BGP Local Routing Information Base MED Advertised to Peer MED Advertised to Peer WITH route-map WITHOUT route-map metric-type internal metric-type internal redistribute isis (IGP cost MED: IGP cost 20 = 20) MED = 20 MED = 0 redistribute isis routemap set metric 50 MED: IGP cost 50 MED: 50 MED: 50 MED: 50 MED: 50 redistribute isis metric 100 MED: IGP cost 100 MED: 100 MED: 100 Ignore Router-ID for Some Best-Path Calculations Dell Networking OS allows you to avoid unnecessary BGP best-path transitions between external paths under certain conditions. The bgp bestpath router-id ignore command reduces network disruption caused by routing and forwarding plane changes and allows for faster convergence. Four-Byte AS Numbers Dell Networking OS supports 4-Byte (32-bit) format when configuring autonomous system numbers (ASNs). The 4-Byte support is advertised as a new BGP capability (4-BYTE-AS) in the OPEN message. If a 4-Byte BGP speaker has sent and received this capability from another speaker, all the messages will be 4-octet. The behavior of a 4-Byte BGP speaker is different with the peer depending on whether the peer is a 4Byte or 2-Byte BGP speaker. Where the 2-Byte format is 1-65535, the 4-Byte format is 1-4294967295. Enter AS numbers using the traditional format. If the ASN is greater than 65535, the dot format is shown when using the show ip bgp commands. For example, an ASN entered as 3183856184 appears in the show commands as 48581.51768; an ASN of 65123 is shown as 65123. To calculate the comparable dot format for an ASN from a traditional format, use ASN/65536. ASN%65536. Traditional Format DOT Format 65001 0.65501 65536 1.0 100000 1.34464 4294967295 65535.65535 When creating Confederations, all the routers in a Confederation must be either 4-Byte or 2-Byte identified routers. You cannot mix them. Border Gateway Protocol IPv4 (BGPv4) 193
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