Large Scale BGP: prefix-lists, default-route & next-hop-self: GNS3 CCNP Lab 1.6: Answers Part 3
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- čas přidán 1. 06. 2018
- GNS3 Portable Project File: bit.ly/2JjtYh6
This is one of multiple Cisco CCNP GNS3 Labs. Are you ready to pass your CCNP exam?
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300-101 ROUTE Exam information: bit.ly/2GkcFXQ
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BGP Route Map Next Hop Self
The BGP Route Map Next Hop Self feature provides a way to override the settings for bgp next-hop unchanged and bgp next-hop unchanged allpath selectively. These settings are global for an address family. For some routes this may not be appropriate. For example, static routes may need to be redistributed with a next hop of self, but connected routes and routes learned via Interior Border Gateway Protocol (IBGP) or Exterior Border Gateway Protocol (EBGP) may continue to be redistributed with an unchanged next hop.
The BGP route map next hop self functionality modifies the existing route map infrastructure to configure a new ip next-hop self setting, which overrides the bgp next-hop unchanged and bgp next-hop unchanged allpaths settings.
The ip next-hop self setting is applicable only to VPNv4 and VPNv6 address families. Routes distributed by protocols other than BGP are not affected.
You configure a new bgp route-map priority setting to inform BGP that the route map will take priority over the settings for bgp next-hop unchanged and bgp next-hop unchanged allpath. The bgp route-map priority setting only impacts BGP. The bgp route-map priority setting has no impact unless you configure the bgp next-hop unchanged or bgp next-hop unchanged allpaths settings.
Route Filtering and Manipulation
Route filtering is a method for selectively identifying routes that are advertised or received from neighbor routers. Route filtering may be used to manipulate traffic flows, reduce memory utilization, or to improve security. For example, it is common for ISPs to deploy route filters on BGP peerings to customers. Ensuring that only the customer routes are allowed over the peering link prevents the customer from accidentally becoming a transit AS on the Internet. Filtering of routes within BGP is accomplished with filter-lists, prefix-lists, or route-maps on IOS and NX-OS devices.
default-information originate (OSPF)
To generate a default external route into an Open Shortest Path First (OSPF) routing domain, use the default-information originate command. To disable this feature, use the no form of this command.
default-information originate [ always ] [ route-map map-name ]
no default-information originate [ always ] [ route-map map-name ]
Border Gateway Protocol (BGP) is a standardized exterior gateway protocol designed to exchange routing and reachability information among autonomous systems (AS) on the Internet. The protocol is classified as a path vector protocol. The Border Gateway Protocol makes routing decisions based on paths, network policies, or rule-sets configured by a network administrator and is involved in making core routing decisions.
BGP may be used for routing within an autonomous system. In this application it is referred to as Interior Border Gateway Protocol, Internal BGP, or iBGP. In contrast, the Internet application of the protocol may be referred to as Exterior Border Gateway Protocol, External BGP, or eBGP.
BGP neighbors, called peers, are established by manual configuration between routers to create a TCP session on port 179. A BGP speaker sends 19-byte keep-alive messages every 60 seconds to maintain the connection. Among routing protocols, BGP is unique in using TCP as its transport protocol.
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Thank you sir it helps a lot!
Great video
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Great that you got BGP working!
Mr. Bombal makes Hollywood series look boring hhh, his series are the best :)
Thank you! Great comment :)
Hello, what is the router IOS you use in the simulation?
thanks for the Encor video series, l have a multihomed lap with 2 ISPs and one enterprise router, l have used “as-path ^$” in BGP to make sure that , the enterprise router is not used as a transit router to other network. before the as-path configuration, haven access to only the enterprise router, what command can l used before the above configuration to see that they enterprise router is not been used as a transit router if l have no access to the peering ISP router.
again friends, using the show bgp ipv4 unicast neighbor 1.1.1.1 (ISP1) and 2.2.2.2 (ISP) advertise-route. is this is only command to be able to determined if my enterprise router is being used as transit routers. can someone clarify on this for me please. thanks in advance !!
I dont know if someone will see this comment but here we go, i configured the prefix list identical to that appear on your video but with the only exception that i put a deny instead of permit keyword. My mind will explote trying to understand why it is still working to filter the routes that i want to filter. In few words using deny or permit have the same result in this lab.
What is denying your routes in the lab? I suppose that is the implicit deny statement.
Shweeet
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