Route Maps ********** Route maps provide a means to both filter and/or apply actions to route, hence allowing policy to be applied to routes. Route maps are an ordered list of route map entries. Each entry may specify up to four distinct sets of clauses: Matching Conditions A route-map entry may, optionally, specify one or more conditions which must be matched if the entry is to be considered further, as governed by the Match Policy. If a route-map entry does not explicitly specify any matching conditions, then it always matches. Set Actions A route-map entry may, optionally, specify one or more Set Actions to set or modify attributes of the route. Matching Policy This specifies the policy implied if the *Matching Conditions* are met or not met, and which actions of the route-map are to be taken, if any. The two possibilities are: * *permit*: If the entry matches, then carry out the *Set Actions*. Then finish processing the route-map, permitting the route, unless an *Exit Policy* action indicates otherwise. * *deny*: If the entry matches, then finish processing the route- map and deny the route (return *deny*). The *Matching Policy* is specified as part of the command which defines the ordered entry in the route-map. See below. Call Action Call to another route-map, after any *Set Actions* have been carried out. If the route-map called returns *deny* then processing of the route-map finishes and the route is denied, regardless of the *Matching Policy* or the *Exit Policy*. If the called route-map returns *permit*, then *Matching Policy* and *Exit Policy* govern further behaviour, as normal. Exit Policy An entry may, optionally, specify an alternative *Exit Policy* to take if the entry matched, rather than the normal policy of exiting the route-map and permitting the route. The two possibilities are: * *next*: Continue on with processing of the route-map entries. * *goto N*: Jump ahead to the first route-map entry whose order in the route-map is >= N. Jumping to a previous entry is not permitted. The default action of a route-map, if no entries match, is to deny. I.e. a route-map essentially has as its last entry an empty *deny* entry, which matches all routes. To change this behaviour, one must specify an empty *permit* entry as the last entry in the route-map. To summarise the above: +----------+----------+------------+ | | Match | No Match | +==========+==========+============+ | Permit | action | cont | +----------+----------+------------+ | Deny | deny | cont | +----------+----------+------------+ action * Apply *set* statements * If *call* is present, call given route-map. If that returns a "deny", finish processing and return "deny". * If *Exit Policy* is *next*, goto next route-map entry * If *Exit Policy* is *goto*, goto first entry whose order in the list is >= the given order. * Finish processing the route-map and permit the route. deny The route is denied by the route-map (return "deny"). cont goto next route-map entry show route-map [WORD] Display data about each daemons knowledge of individual route-maps. If WORD is supplied narrow choice to that particular route-map. clear route-map counter [WORD] Clear counters that are being stored about the route-map utilization so that subsuquent show commands will indicate since the last clear. If WORD is specified clear just that particular route-map's counters. Route Map Command ================= route-map ROUTE-MAP-NAME (permit|deny) ORDER Configure the *order*'th entry in *route-map-name* with "Match Policy" of either *permit* or *deny*. Route Map Match Command ======================= match ip address ACCESS_LIST Matches the specified *access_list* match ip address prefix-list PREFIX_LIST Matches the specified *PREFIX_LIST* match ip address prefix-len 0-32 Matches the specified *prefix-len*. This is a Zebra specific command. match ipv6 address ACCESS_LIST Matches the specified *access_list* match ipv6 address prefix-list PREFIX_LIST Matches the specified *PREFIX_LIST* match ipv6 address prefix-len 0-128 Matches the specified *prefix-len*. This is a Zebra specific command. match ip next-hop IPV4_ADDR Matches the specified *ipv4_addr*. match as-path AS_PATH Matches the specified *as_path*. match metric METRIC Matches the specified *metric*. match tag TAG Matches the specified tag value associated with the route. This tag value can be in the range of (1-4294967295). match local-preference METRIC Matches the specified *local-preference*. match community COMMUNITY_LIST Matches the specified *community_list* match peer IPV4_ADDR This is a BGP specific match command. Matches the peer ip address if the neighbor was specified in this manner. match peer IPV6_ADDR This is a BGP specific match command. Matches the peer ipv6 address if the neighbor was specified in this manner. match peer INTERFACE_NAME This is a BGP specific match command. Matches the peer interface name specified if the neighbor was specified in this manner. match source-protocol PROTOCOL_NAME This is a ZEBRA specific match command. Matches the originating protocol specified. match source-instance NUMBER This is a ZEBRA specific match command. The number is a range from (0-255). Matches the originating protocols instance specified. Route Map Set Command ===================== set tag TAG Set a tag on the matched route. This tag value can be from (1-4294967295). Additionally if you have compiled with the "-- enable-realms" configure option. Tag values from (1-255) are sent to the Linux kernel as a realm value. Then route policy can be applied. See the tc man page. set ip next-hop IPV4_ADDRESS Set the BGP nexthop address to the specified IPV4_ADDRESS. For both incoming and outgoing route-maps. set ip next-hop peer-address Set the BGP nexthop address to the address of the peer. For an incoming route-map this means the ip address of our peer is used. For an outgoing route-map this means the ip address of our self is used to establish the peering with our neighbor. set ip next-hop unchanged Set the route-map as unchanged. Pass the route-map through without changing it's value. set ipv6 next-hop peer-address Set the BGP nexthop address to the address of the peer. For an incoming route-map this means the ipv6 address of our peer is used. For an outgoing route-map this means the ip address of our self is used to establish the peering with our neighbor. set ipv6 next-hop prefer-global For Incoming and Import Route-maps if we receive a v6 global and v6 LL address for the route, then prefer to use the global address as the nexthop. set ipv6 next-hop global IPV6_ADDRESS Set the next-hop to the specified IPV6_ADDRESS for both incoming and outgoing route-maps. set local-preference LOCAL_PREF Set the BGP local preference to *local_pref*. set weight WEIGHT Set the route's weight. set metric METRIC Set the BGP attribute MED. set as-path prepend AS_PATH Set the BGP AS path to prepend. set community COMMUNITY Set the BGP community attribute. set ipv6 next-hop local IPV6_ADDRESS Set the BGP-4+ link local IPv6 nexthop address. set origin ORIGIN Set BGP route origin. Route Map Call Command ====================== call NAME Call route-map *name*. If it returns deny, deny the route and finish processing the route-map. Route Map Exit Action Command ============================= on-match next continue Proceed on to the next entry in the route-map. on-match goto N continue N Proceed processing the route-map at the first entry whose order is >= N Route Map Examples ================== A simple example of a route-map: route-map test permit 10 match ip address 10 set local-preference 200 This means that if a route matches ip access-list number 10 it's local-preference value is set to 200. See Miscellaneous Configuration Examples for examples of more sophisticated usage of route-maps, including of the "call" action.