eBGP

باسلام

امروز یک سناریو دیگه رو آماده کردم

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You will notice that all the IP addressing schemes are /24, except for the serial link between R1 and R2. The serial link contains a mask, 255.255.255.252 or /30. BGP has no issues with VLSM. The 16 loopbacks on R1 are advertised to R2 using the redistribute connected command. The no-auto summary command ensures that R2 sees all 16 individual routes. The access list on R2 must be set with a mask of 0.0.254.255, or all even networks match these criteria. The dual-path connections between R1 and R2 allow redundancy. There are two EBGP sessions between R1 and R2; therefore, the route map on R2 is applied to both EBGP peers in case of link failure.

شکل شبیه سازی شده سناریوی

BGP community

سلام

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R1 is configured for EBGP and IBGP. The EBGP connection to the remote peer address, 141.199.2.2, is the Internet gateway. Therefore, you must send the
community to the remote peer and apply an outbound route map, so the Internetrouters do not use R1 as a transit path. You have yet to apply the route map named setcommunity (arbitrary name).  Apply the well-known community no-export, which informs the neighboring router not to use R1 for any traffic not destined for the network 131.108.0.0/16.

configure the four routers, R1–R4, for IBGP, and set the same policies on all four routers.

ensure that R1 does not receive any default routes from R2, R3, or R4 (sets the next-hop-self attribut. Ensure that R1 sets the community to the value 2000.

R1(config)#route-map setcommunity

R1(config-route-map)#set community no-export
R1(config-router)#neighbor 141.199.2.2 route-map setcommunity out

یعنی مسیرهایی که با این مقدار دریافت میشوند،دیگر به همسایه های eBGP تبلیغ نشوند.یعنی به روتر 5 هیچ مسیری از AS1 تبلیغ نشود.

سناریو BGP

All routers have a loopback 0 interface X.X.X.X/32 where X is the number of the router.
Configure OSPF on R1, R2, R3 and advertise 10.10.12.0/24, 10.10.13.0/24 and loopback 0 subnets
Configure OSPF on R4, R5 and advertise 150.45.45.0/26 and loopback 0 subnets
Configure full iBGP mesh in AS 123, use loopback 0 interface for peering
Configure iBGP in AS 45, use loopback 0 interface for peering
Configure eBGP between AS 123 and AS 45
Advertise R1 loopback 0 and 150.45.45.0/26 in BGP
Ensure AS 123 will use the link between R3-R5 towards network 150.45.45.0/26. Use MED attribute only.
Ensure AS 45 will use the link between R3-R5 towards network 1.1.1.1/32. Use MED attribute only.