Allied Telesis X908 manual

Te c h n i c a l G u i d e alliedtelesis .com x How T o | C613-16128-00 REV E Introduction ISPs tr anspor t lar ge volumes of data. They often ha ve to pa y lar ge amounts of money to tr anspor t their data through hired links, or thro ugh other pro vider s' networ ks. Similar ly , they can also char ge money for transpor ting other ISPs'[...]

I n tr od 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 . ............ ............... ............ ............ ............ ............ ............... ............ ............ ................. ............. ............ ............ ............ ............ ....[...]

Use Ro u te Ma ps 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 Fil teri ng Example ... ............ ............ ............... ............ ............ ............... ............ .. ....... ............... ........... ........... ............... ....48 BGP configur ation ..........[...]

BGP: Co n cepts a n d T ermi n olog y 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 T er minology Before mo vi ng on to look at the filtering proc esses, it is impor tant to fir st hav e some under st anding of cer tain aspects of how BG P w or ks. The follo wing sections describe: [...]

Use Ro u te Ma ps a n d Other Filters to Filter a n d Alter BGP a n d OS PF Ro u tes | Page 5 BGP: Co n cepts a n d T ermi n olog y Update attr ib u tes As mentioned abo ve , each BGP up date message contains a set of attr ibut es. These attr ibut es descr ibe some of the proper ties of the routes , and can be used in making decisions about which r[...]

BGP: Overview of t he Available Filter T ypes 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: Ov er view of the A vailab le Filter T ypes The following sections describe the var ious types of filter s that can be applied to BGP updates and the hierarchy of the filters. Filter types There are a number[...]

K EY W ORD IN COMMAND DEFINABLE FILTER WA Y TO APPLY FIL TERING AC L access-list Ye s Distribute list distr ibute-list Ye s Prefix list prefix-list Ye s Ye s AS path list as-pat h Ye s Filter list filter -list Ye s Route map route-map Ye s Ye s Use Ro u te Ma ps a n d Other Filters to Filter a n d Alter BGP a n d OS PF Ro u tes | Page 7 BGP: Ov er [...]

Hierarch y of the Di ffere 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 Hier archy of the Diff erent Filter s For distr ibute filter s (A CLs), path filter s, and prefix filter s, the order of application is not impor tant. If an update is denied by an y given f ilter , it is discarded imm [...]

Use Ro u te Ma ps a n d Other Filters to Filter a n d Alter BGP a n d OS PF Ro u tes | Page 9 Hierar ch y of the Differ e n t Filters Basic co n fig u ratio n This configuration gets the neighbor relationship establis hed and some routes exchanged. AlliedW are Plus switch Create the second VLAN an d associate por t 1 .0.2 with it; assign IP address[...]

Hierarch y of the Di ffere n t Filters Page 10 | Use Ro u te Ma ps 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 r elatio n ship Check that each switch sees the interface rout e adver tised from the other switch. On both the AlliedW are Plus and AlliedW a re switches, use the c ommand sho w ip rout e[...]

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: Configur ing Distr ibute Filter s Distr ibute f ilter s use A CLs (Access Control Lists) to filter par ticular routes on the ba sis of their prefix es. Distr ibute filters and prefix filt er s both filter ind[...]

BGP: Co n fig u ri n g Dis trib u te Filters Page 12 | Use Ro u te Ma ps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes Usi n g A CLs as filters When y ou ha ve created an A CL, y ou can use it to filter incoming or outgoing update messages for a par ticular BGP peer , by using the follo wing commands in BGP router mode for t he [...]

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 pref ix le n gths This example demonstrates the effect of the exact par ameter in the A CL by discarding all routes to 52.0.0.0 with pr efix length s of 4 or greater . 3. Renew the route [...]

BGP: Co n fig u ri n g Dis trib u te Filters Page 14 | Use Ro u te Ma ps 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 r oute table now includes all the r outes. awplus(config-router)# do show ip route Codes: C - connected, S - static, R - RI P, B [...]

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 A CL i n stead of a n amed A CL This example demonstrates a numbered A CL by discarding all routes to 52.0.0.0. In line with industr y standards, the wildcard mask is required but its val ue has no[...]

BGP: Co n fig u ri n g Dis trib u te Filters Page 16 | Use Ro u te Ma ps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes 4. Check that the IP r oute table no longer includes 52.0.0.0/8. awplus(config-router)# do show ip route Codes: C - connected, S - static, R - RI P, B - BGP O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external[...]

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: Configur ing AS P ath Filter s T o configure path filters we need to fir st under stand something about AS path lists and how to use them. AS path lists Path f i lter s use a constr uct known as an AS path list . [...]

BGP: Co n fig u ri n g AS Path Filters Page 18 | Use Ro u te Ma ps 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 , by using the following commands in BGP router [...]

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)# neighbor 45.45.45.46 no shutdown 5. Check that the IP r [...]

AS path access list list1 deny 23456 permit 34568 BGP: Co n fi g u ri n g AS Path Filters Page 20 | Use Ro u te Ma ps 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 filt er tha t u ses an AS-path list ip as-path access-list example deny ^$ ip as-path access-list example permit 34567 neighbor 45.45.45[...]

BGP route table Flags: >=Best route for the gi ven prefix, *=Unreachable next hop, W=Withdrawn m=Community, a=Aggregate route, s=Aggregate Suppresse d, D=Damped Learned from: L=Local, e=eBGP Peer, i=iBGP Peer, c=Confederate Peer ------------------------------ --------------------------------------- Fl Prefix Next hop Origin MED Local pref Path O[...]

BGP: Co n fig u ri n g Pref ix Filters Page 22 | Use Ro u te Ma ps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes BGP: Configur ing Prefix Filter s Prefix filters use prefix lists to filter par t icular routes on the basis of the ir prefix es. Prefix fi lter s and distr ibute filter s both filter individual routes out of BGP upda[...]

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 Pref ix Filters Usi n g pr efix lists as pr efix filters When y ou ha ve created a pref ix list, you can us e it to filter incoming or outgoing update messages for a par ticular BGP peer , by using the following commands in BGP router[...]

BGP: Co n fig u ri n g Pref ix Filters Page 24 | Use Ro u te Ma ps 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 differ e n t prefix le n gths This example f ilter s out routes to 45.0.0.0 w ith prefix le ngths in the range 5-8, accepts routes to 52.0.0.0/8, and implicitly filter s out all other BGP rou[...]

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 25 BGP: Co n fig u ri n g Pref ix Filters 5. Check that the IP r oute table now cont ains only the other r oute from the neighbor . awplus(config-router)# do show ip route Codes: C - connected, S - static, R - RIP, B - BGP O - OSPF, IA - OSPF inter ar ea N1 - [...]

BGP: Co n fig u ri n g Ro u te Maps Page 26 | Use Ro u te Ma ps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes BGP: Configur ing Route Maps Route maps are ver y pow erful and flexib le entities. Therefore, the configuring of route maps must, b y necessity , be relatively complex. The pur pose of this section of the document is to[...]

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 a ttr ibutes or prefixes to match on  set cla u ses , which specify the changes to be made to attr[...]

BGP: Co n fig u ri n g Ro u te Maps Page 28 | Use Ro u te Ma ps 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 con f igur ation s would cause outgoing updat e packets with emp ty AS paths to be dropped, and update packet s with an AS path containing 15557 to be allowed. But, to achieve that in the se[...]

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 specif y the communities. They can be identif ied by a number , or by the word expa n ded , an d are created b y using any of the f ollo wing commands: Y ou can hav e multiple ent[...]

BGP: Co n fig u ri n g Ro u te Maps Page 30 | Use Ro u te Ma ps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes O n c e y o u h a ve m a d e t h e AC L , a p p l y i t t o t h e m a t c h c l a u s e o f a r o u t e m a p e n t r y by u s i n g t h e command: A n ext hop addr ess Y ou can use either a prefix list or an A CL to spe[...]

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 Comm unity set clauses give y ou a lot of control ov er the commun ity values in updates. Yo u c a n :  Replace the set of comm unity values in an update , by usin g the command: set community < community-[...]

BGP: Co n fig u ri n g Ro u te Maps Page 32 | Use Ro u te Ma ps 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 attr ibute to the update . Use the command: set atomic-aggregate Extended community This specifies a value to set as the Extended Community attribute in the update message[...]

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 di ffer e n t comb i 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, or  one match clause and one or more se[...]

BGP: Co n fig u ri n g Ro u te Maps Page 34 | Use Ro u te Ma ps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes P ar ticular mention, though, has to be made of the case where the match clause specifies prefix list or A CL as the match cr iter ion, and the route ma p is being applied to outgoing route updates. The intention of such[...]

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, Pr efix, a n d Ro u te Map Fi lters to a Peer BGP: Applying Distr ib ute , Path, Pref ix, and Route Map Filter s to a P eer Distr ibute filter s, path filter s, prefix filter s, and route m aps can all be applied to a BGP[...]

Examples Page 36 | Use Ro u te Ma ps 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 ma p that matches o n a pre fix-list a n d sets the r o u te metrics 1. Create a pref ix list that matches just 52.0 .0.0/8 awplus(config)# ip prefix-list test1 permit 52.0.0.0/8 2. Then, create a ro ute map to match o[...]

Codes: C - connected, S - stat ic, R - RIP, B - BGP O - OSPF, IA - OSPF int er 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 ly connected, vlan1 C 64.0.0.0/4 is directly co[...]

Examples Page 38 | Use Ro u te Ma ps 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 matche s on the neighbor's IP address: awplus# ship prefix-list nh-test permit 45.45.45.46/32 2. Create a route map with a permit entr y that matches on this prefi[...]

BGP route table Flags: >=Best route for the gi ven prefix, *=Unreachable next hop, W=Withdrawn m=Community, a=Aggregate route, s=Aggregate Suppresse d, D=Damped Learned from: L=Local, e=eBGP Peer, i=iBGP Peer, c=Confederate Peer ------------------------------ --------------------------------------- Fl Prefix Next hop Origin MED Local pref Path O[...]

Examples Page 40 | Use Ro u te Ma ps 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 criter io n on a per mit 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 b y this route map , we can b e sure that it was droppe d by the[...]

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=45.45.45.45 outroutemap=mixed sendcommunity=yes Whe[...]

Examples Page 42 | Use Ro u te Ma ps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes With this combination, neither 156.23 .4.32/27 nor 156.34 .4.144/28 appear in the IP route table. The route 15 6.23.4.32/27 is droppe d by the route map f ilter , and the route 156.34.4.144 /28 is dropped by the ASPath-list filter . 7. Now create [...]

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 A CL-match i n a ro u te ma p to u pdate j u st a si n gle r o u te o u t of a n u pdate 1. Configure static r outes on the A W+ switch. BGP(config)# ip route 192.34.23.0/26 64.93.23.1 BGP(config)# ip route 192.34.23.32/29 64.[...]

BGP route table Flags: >=Best route for th e given prefix, *=Unreachable next hop, W=Withdrawn m=Community, a=Aggregate route, s=Aggregate Suppr essed, D=Damped Learned from: L=Local, e=eBGP Peer, i=iBGP Peer, c=Confederate P eer -------------------------- ------------------------------------------- Fl Prefix Next hop Origin MED Local pref Path [...]

W a ys to u se lists i n IP ro u te f ilteri ng f or BGP , with g e n eric co mm a n d exa m ples Path f ilters ip as-path access-list <aslist1> ... ... per m it <re g -ex> ... de n y <re g -ex> ... per m it <re g -ex> ip as-path access-list <aslist2> ... ... per m it <re g -ex> ... de n y <re g -ex> Pre f [...]

BGP: Applyi n g Ro u te Maps to Imported Ro u tes Page 46 | Use Ro u te Ma ps 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 w o uld be static rout es, or routes learnt by OSPF or [...]

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 filter ing routes. Let us look br iefly at some of the other contexts in which they are used. n eighbor defa u lt-origi n ate The command neighbor default-or[...]

BGP: Ro u te Ma p Filteri n g Example Page 48 | Use Ro u te Ma ps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes BGP: Route Map Filter ing Example Here is an example of a set of route maps. BGP co n fig u ratio n Fir st, we need to set the router’ s ASN and the ASN of the peer . router bgp 3816 neighbor 172.26.1.1 remote-as 155[...]

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 49 BGP: Ro u te Map Filter i n g Example set local-preference 9000 route-map outdef permit 3 match ip address prefix-list plist4 set as-path prepend 64751 1827 set community no-export additive set local-preference 9000 route-map outdef permit 4 router bgp 3816[...]

OSPF: Co n fig u ri n g Ro u te Maps f or Filter i n g a n d Modifyi n g OSPF Ro u tes Page 50 | Use Ro u te Ma ps a n d Other Filters to Filter a n d Alter BGP a n d OSPF Ro u tes OSPF: Configuring Route Maps for Filter ing and Modifying OSPF Routes For information about route maps and their str ucture , see "Str ucture of a route map" o[...]

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 Modif yi n g OSPF Ro u tes Exter n al r o u te type The entr y will match all routes of either T ype 1 Exter nal or Ty p e 2 E x t e r n a l . T o match a route type , use the command : match extern[...]

C613-16128-00 REV E North A m erica Headquarters | 19 8 0 0 N or t h C re e k Par k w ay | S u i te 10 0 | Bot he ll | WA 9 8 01 1 | USA | T: +1 8 0 0 424 42 8 4 | F: + 1 42 5 4 8 1 3 8 95 Asia -Paci  c Headq uarters | 1 1 T a i Se n g Li n k | Si n ga p ore | 5341 8 2 | T : +6 5 63 8 3 3 8 32 | F: +65 63 8 3 3 8 30 EM E A & C SA O pe r ati [...]