Page 2 - Co
I n trod u ctio n Page 2 | Use Ro u te Maps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes Co n te n ts Introduction .......................................................................................................................................................................
Page 3 - Related How To Notes; How To Use Route Maps and Other Filters to Filter and Alter BGP and; Which prod; AlliedWare Prod
Use Ro u te Maps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes | Page 3 I n trod u ctio n BGP: Route Map Filtering Example ................................................................................................................................................................
Page 4 - BGP: Concepts and Terminology; BGP peers; Definition; Definition; and
BGP: Co n cepts a n d Termi n ology Page 4 | Use Ro u te Maps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes BGP: Concepts and Terminology Before moving on to look at the filtering processes, it is impor tant to first have some understanding of cer tain aspects of how BGP works. T...
Page 5 - Update attrib; Origi
Use Ro u te Maps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes | Page 5 BGP: Co n cepts a n d Termi n ology Update attrib u tes As mentioned above, each BGP update message contains a set of attributes. These attributes describe some of the proper ties of the routes, and can be us...
Page 6 - BGP: Over view of the Available Filter Types; Filter types
BGP: Overview of the Available Filter Types Page 6 | Use Ro u te Maps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes BGP: Over view of the Available Filter Types The following sections describe the various types of filters that can be applied to BGP updates and the hierarchy of th...
Page 8 - Hierarchy of the Different Filters
Hierarchy of the Differe n t Filters Page 8 | Use Ro u te Maps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes Hierarchy of the Different Filters For distribute filters (ACLs), path filters, and prefix filters, the order of application is not impor tant. If an update is denied by a...
Page 9 - Basic co; AlliedWare Plus
Use Ro u te Maps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes | Page 9 Hierarchy of the Differe n t Filters Basic co n fig u ratio n This configuration gets the neighbor relationship established and some routes exchanged. AlliedWare Plus switch Create the second VLAN and associa...
Page 10 - show ip route
Hierarchy of the Differe n t Filters Page 10 | Use Ro u te Maps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes Co n firmi n g the n eighbor relatio n ship Check that each switch sees the interface route adver tised from the other switch. On both the AlliedWare Plus and AlliedWare ...
Page 11 - BGP: Configuring Distribute Filters; Abo; deny; or; permit; Named ACLs
Use Ro u te Maps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes | Page 11 BGP: Co n fig u ri n g Distrib u te Filters BGP: Configuring Distribute Filters Distribute filters use ACLs (Access Control Lists) to filter par ticular routes on the basis of their prefixes. Distribute filt...
Page 12 - Usi; permit any
BGP: Co n fig u ri n g Distrib u te Filters Page 12 | Use Ro u te Maps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes Usi n g ACLs as filters When you have created an ACL, you can use it to filter incoming or outgoing update messages for a par ticular BGP peer, by using the follow...
Page 13 - Filter o; This example demonstrates the effect of the; exact; parameter in the ACL by discarding all
Use Ro u te Maps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes | Page 13 BGP: Co n fig u ri n g Distrib u te Filters Filter o u t a ra n ge of prefix le n gths This example demonstrates the effect of the exact parameter in the ACL by discarding all routes to 52.0.0.0 with prefix ...
Page 14 - Check that the IP route table now includes all the routes.; is not specified, the ACL entry
BGP: Co n fig u ri n g Distrib u te Filters Page 14 | Use Ro u te Maps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes Set that ACL as the filter for the BGP neighbor 45.45.45.46: 3. Check that the IP route table now includes all the routes. awplus(config-router)# do show ip route ...
Page 15 - Use a
Use Ro u te Maps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes | Page 15 BGP: Co n fig u ri n g Distrib u te Filters Use a nu mbered ACL i n stead of a n amed ACL This example demonstrates a numbered ACL by discarding all routes to 52.0.0.0. In line with industr y standards, the ...
Page 17 - BGP: Configuring AS Path Filters; AS path lists; Path filters use a construct known as an; For example, you can specify things like:
Use Ro u te Maps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes | Page 17 BGP: Co n fig u ri n g AS Path Filters BGP: Configuring AS Path Filters To configure path filters we need to first understand something about AS path lists and how to use them. AS path lists Path filters use...
Page 18 - Example: AS path filters; Discard or allow ro; Implicitly; If you previously configured a distribute filter, as shown in
BGP: Co n fig u ri n g AS Path Filters Page 18 | Use Ro u te Maps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes Usi n g AS path lists as path filters When an AS path list has been created, it can be applied to filter incoming or outgoing update messages for a par ticular BGP peer...
Page 19 - Explicitly include; Shut down the neighbor, and then bring it up again.
Use Ro u te Maps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes | Page 19 BGP: Co n fig u ri n g AS Path Filters Explicitly include a neighbor 4. Shut down the neighbor, and then bring it up again. awplus(config-router)# neighbor 45.45.45.46 shutdown awplus(config-router)# neighbo...
Page 20 - other example; An outgoing; Check that the AS path list shows the two filter entries:
AS path access list list1 deny 23456 permit 34568 BGP: Co n fig u ri n g AS Path Filters Page 20 | Use Ro u te Maps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes A n other example An outgoing filter that uses an AS-path list ip as-path access-list example deny ^$ ip as-path acces...
Page 22 - BGP: Configuring Prefix Filters; not; A prefix list entr y is created with the command:; Mask le; If you set the mask length to:
BGP: Co n fig u ri n g Prefix Filters Page 22 | Use Ro u te Maps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes BGP: Configuring Prefix Filters Prefix filters use prefix lists to filter par ticular routes on the basis of their prefixes. Prefix filters and distribute filters both f...
Page 23 - This example expands on the basic configuration in
Use Ro u te Maps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes | Page 23 BGP: Co n fig u ri n g Prefix Filters Usi n g prefix lists as prefix filters When you have created a prefix list, you can use it to filter incoming or outgoing update messages for a par ticular BGP peer, by ...
Page 24 - g prefix list e
BGP: Co n fig u ri n g Prefix Filters Page 24 | Use Ro u te Maps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes Filter o u t a ra n ge of differe n t prefix le n gths This example filters out routes to 45.0.0.0 with prefix lengths in the range 5-8, accepts routes to 52.0.0.0/8, an...
Page 26 - BGP: Configuring Route Maps; Str; There are various levels of structure within a route map:
BGP: Co n fig u ri n g Ro u te Maps Page 26 | Use Ro u te Maps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes BGP: Configuring Route Maps Route maps are ver y powerful and flexible entities. Therefore, the configuring of route maps must, by necessity, be relatively complex. The pu...
Page 27 - match cla; AS path list; For information about creating an AS path list, see
Use Ro u te Maps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes | Page 27 BGP: Co n fig u ri n g Ro u te Maps Cla u ses There are two types of clauses that can be present in a route map entr y: match cla u ses , which specify attributes or prefixes to match on set cla u ses , ...
Page 28 - A comm; Creating; standard
BGP: Co n fig u ri n g Ro u te Maps Page 28 | Use Ro u te Maps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes Case 1: Case 2: Both of these configurations would cause outgoing update packets with empty AS paths to be dropped, and update packets with an AS path containing 15557 to ...
Page 29 - expa; For information about creating a prefix list, see; e or more prefixes, by; expanded
Use Ro u te Maps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes | Page 29 BGP: Co n fig u ri n g Ro u te Maps Expanded lists use regular expressions to specify the communities. They can be identified by a number, or by the word expa n ded , and are created by using any of the foll...
Page 30 - ext hop address; If a packet matches the; match; clause, then the action of the route map entr y will be applied; set; AS path
BGP: Co n fig u ri n g Ro u te Maps Page 30 | Use Ro u te Maps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes Once you have made the ACL, apply it to the match clause of a route map entr y by using the command: A n ext hop address You can use either a prefix list or an ACL to spec...
Page 31 - Community; ) and then applying it in a set; Origin
Use Ro u te Maps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes | Page 31 BGP: Co n fig u ri n g Ro u te Maps Community Community set clauses give you a lot of control over the community values in updates. You can: Replace the set of community values in an update, by using the c...
Page 32 - rt
BGP: Co n fig u ri n g Ro u te Maps Page 32 | Use Ro u te Maps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes Atomic- aggregate This adds the atomic aggregate attribute to the update. Use the command: set atomic-aggregate Extended community This specifies a value to set as the Ext...
Page 33 - The effect of differe; A map entr y could consist of:
Use Ro u te Maps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes | Page 33 BGP: Co n fig u ri n g Ro u te Maps The effect of differe n t combi n atio n s of cla u ses A map entr y could consist of: one match clause with an action, or no match clause and one or more set clauses,...
Page 34 - ly
BGP: Co n fig u ri n g Ro u te Maps Page 34 | Use Ro u te Maps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes Par ticular mention, though, has to be made of the case where the match clause specifies prefix list or ACL as the match criterion, and the route map is being applied to o...
Page 35 - First, enter BGP router mode for the AS. The prompt should look like:
Use Ro u te Maps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes | Page 35 BGP: Applyi n g Distrib u te, Path, Prefix, a n d Ro u te Map Filters to a Peer BGP: Applying Distribute, Path, Prefix, and Route Map Filters to a Peer Distribute filters, path filters, prefix filters, and r...
Page 36 - Examples; Example A
Examples Page 36 | Use Ro u te Maps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes Examples Example A A ro u te map that matches o n a prefix-list a n d sets the ro u te metrics 1. Create a prefix list that matches just 52.0.0.0/8 awplus(config)# ip prefix-list test1 permit 52.0.0...
Page 37 - Example C; un
Codes: C - connected, S - static, R - RIP, B - BGP O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2 * - candidate default B 45.0.0.0/8 [20/665] via 45.45.45.46, vlan1, 00:00:02 C 45.45.45.0/24 is direct...
Page 38 - Example D; Example E; nu; Shut down the neighbor, and then bring it up again:
Examples Page 38 | Use Ro u te Maps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes Example D Matchi n g o n a n ext-hop prefix-list 1. Create a prefix-list that matches on the neighbor's IP address: awplus# ship prefix-list nh-test permit 45.45.45.46/32 2. Create a route map with ...
Page 39 - Example G; Configure the AW peer to send out a community number 89:89
BGP route table Flags: >=Best route for the given prefix, *=Unreachable next hop, W=Withdrawn m=Community, a=Aggregate route, s=Aggregate Suppressed, D=Damped Learned from: L=Local, e=eBGP Peer, i=iBGP Peer, c=Confederate Peer --------------------------------------------------------------------- ...
Page 40 - Example H; Configure the peer to give Community 89:89 to the route
Examples Page 40 | Use Ro u te Maps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes 4. Set the prefix-list to be the match criterion on a permit entr y in the route map: route-map com permit 2 match ip address prefix-list test1 If the route 52.0.0.0/8 is dropped by this route map, ...
Page 41 - When the route
Use Ro u te Maps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes | Page 41 Examples add ip routem=mixed entry=1 match prefixlist=com add ip routem=mixed entry=1 set com=89:89 add ip routem=mixed entry=2 match prefixlist=as add ip routem=mixed entry=2 set aspath=34599 set bgp peer=4...
Page 43 - Example I; Apply this route map as the out route map for the peer.
Use Ro u te Maps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes | Page 43 Examples Example I Usi n g a n ACL-match i n a ro u te map to u pdate j u st a si n gle ro u te o u t of a n u pdate 1. Configure static routes on the AW+ switch. BGP(config)# ip route 192.34.23.0/26 64.93.2...
Page 46 - BGP: Applying Route Maps to Impor ted Routes; The switch uses the route map to:; Sy
BGP: Applyi n g Ro u te Maps to Imported Ro u tes Page 46 | Use Ro u te Maps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes BGP: Applying Route Maps to Impor ted Routes The switch is able to impor t routes into BGP that it learnt by non-BGP means. In other words, the routes would ...
Page 47 - Other Uses of Route Maps; eighbor defa; etwork; if; show ip bgp
Use Ro u te Maps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes | Page 47 Other Uses of Ro u te Maps Other Uses of Route Maps Route maps are used in some contexts other than filtering routes. Let us look briefly at some of the other contexts in which they are used. n eighbor defa ...
Page 48 - BGP: Route Map Filtering Example; Here is an example of a set of route maps.
BGP: Ro u te Map Filteri n g Example Page 48 | Use Ro u te Maps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes BGP: Route Map Filtering Example Here is an example of a set of route maps. BGP co n fig u ratio n First, we need to set the router’s ASN and the ASN of the peer. router ...
Page 50 - cannot; Metric; To match a metric value, use the command:; terface
OSPF: Co n fig u ri n g Ro u te Maps for Filteri n g a n d Modifyi n g OSPF Ro u tes Page 50 | Use Ro u te Maps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes OSPF: Configuring Route Maps for Filtering and Modifying OSPF Routes For information about route maps and their structure,...
Page 51 - The entr y will match one or more route prefixes.; If a route matches the; The prompt should look like:
Use Ro u te Maps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes | Page 51 OSPF: Co n fig u ri n g Ro u te Maps for Filteri n g a n d Modifyi n g OSPF Ro u tes Exter n al ro u te type The entr y will match all routes of either Type 1 External or Type 2 External. To match a route ty...
Page 52 - Next hop; Type; OSPF: Applying Route Maps; Use commands like the following:
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