Dell PowerSwitch S4820T 9.50.1 Configuration Guide for the S4820T System - Page 214

to affect interdomain routing. By identifying certain ASN in the AS_PATH, you can permit or deny routes based on the number in its AS_PATH. AS-PATH ACLs use regular expressions to search AS_PATH values. AS-PATH ACLs have an "implicit deny." This means that routes that do not meet a deny or match filter are dropped. To configure an AS-PATH ACL to filter a specific AS_PATH value, use these commands in the following sequence. 1. Assign a name to a AS-PATH ACL and enter AS-PATH ACL mode. CONFIGURATION mode ip as-path access-list as-path-name 2. Enter the parameter to match BGP AS-PATH for filtering. CONFIG-AS-PATH mode {deny | permit} filter parameter This is the filter that is used to match the AS-path. The entries can be any format, letters, numbers, or regular expressions. You can enter this command multiple times if multiple filters are desired. For accepted expressions, refer to Regular Expressions as Filters. 3. Return to CONFIGURATION mode. AS-PATH ACL mode exit 4. Enter ROUTER BGP mode. CONFIGURATION mode router bgp as-number 5. Use a configured AS-PATH ACL for route filtering and manipulation. CONFIG-ROUTER-BGP mode neighbor {ip-address | peer-group-name} filter-list as-path-name {in | out} If you assign an non-existent or empty AS-PATH ACL, the software allows all routes. Example of the show ip bgp paths Command To view all BGP path attributes in the BGP database, use the show ip bgp paths command in EXEC Privilege mode. Dell#show ip bgp paths Total 30655 Paths Address Hash Refcount Metric Path 0x4014154 0 3 18508 701 3549 19421 i 0x4013914 0 3 18508 701 7018 14990 i 0x5166d6c 0 3 18508 209 4637 1221 9249 9249 i 0x5e62df4 0 2 18508 701 17302 i 0x3a1814c 0 26 18508 209 22291 i 0x567ea9c 0 75 18508 209 3356 2529 i 0x6cc1294 0 2 18508 209 1239 19265 i 214 Border Gateway Protocol IPv4 (BGPv4)