Poland
GRANDMETRIC Sp. z o.o.
ul. Metalowa 5, 60-118 Poznań, Poland
NIP 7792433527
+48 61 271 04 43
info@grandmetric.com
Sweden
Drottninggatan 86
111 36 Stockholm
+46 762 041 514
info@grandmetric.com
UK
Grandmetric LTD
Office 584b
182-184 High Street North
London
E6 2JA
+44 20 3321 5276
info@grandmetric.com
US Region
Grandmetric LLC
Lewes DE 19958
16192 Coastal Hwy USA
EIN: 98-1615498
+1 302 691 94 10
info@grandmetric.com
Technology: Routing
Area: IGP
Vendor: Cisco
Software: 12.X , 15.X, IP Base, IP Services
Platform: Catalyst 3560, 3750, 3850, 4500, 6500, ISR Routers
Functionality of Local Autonomous System allows to hide currently used AS number. Command instructs router to include local AS number in BGP OPEN message instead of AS number specified at routing process. This could be really helpful especially during the AS migration.
To configure example BGP process that use 200 AS number instead of AS 100 to connect with “CompanyB” neighbor, use the following command:
CompanyA#configure terminal
CompanyA(config)#router bgp 100
CompanyA(config-router)# neighbor 80.50.0.1 remote-as 101
CompanyA(config-router)# neighbor 80.50.0.1 local-as 200 [no-prepend replace-as dual-as]
CompanyA(config-router)# neighbor 80.50.0.1 description CompanyB
CompanyA(config-router)#exit
Verification commands:
CompanyA#show bgp ipv4 unicast summary
Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
80.50.0.1 4 101 5 5 3 0 0 00:01:39 1
CompanyA#show bgp ipv4 unicast neighbors 80.50.0.1
BGP neighbor is 80.50.0.1, remote AS 101, local AS 200, external link
Description: CompanyB
CompanyA#show bgp ipv4 unicast
Network Next Hop Metric LocPrf Weight Path
*> 80.80.1.0/24 80.50.0.1 0 0 200 101 i
*> 80.80.2.0/24 0.0.0.0 0 32768 i
Extensions:
Command offers a couple of keyword extensions to influence a final result:
A. no-prepend – prefixes received from eBGP peer will not have a Local Autonomous System number prepended in our example AS 200.
Verification commands:
CompanyA#show bgp ipv4 unicast
Network Next Hop Metric LocPrf Weight Path
*> 80.80.1.0/24 80.50.0.1 0 0 101 i
*> 80.80.2.0/24 0.0.0.0 0 32768 i
B. replace-as – prefixes advertised to eBGP peer will not have real process AS number prepended in our example AS 100.
Verification commands:
CompanyB#show bgp ipv4 unicast
Network Next Hop Metric LocPrf Weight Path
*> 80.80.1.0/24 0.0.0.0 0 32768 i
*> 80.80.2.0/24 80.50.0.2 0 0 200 i
C. dual-as – used to establish BGP peering using local or real AS numbers.