Exterior Border Gateway Protocol (eBGP)
eBGP Fundamentals
- Connecting to a different AS (Autonomous System)
- Directly attached (no more than 1 hop)
- Advertising Router is set to next hop
- Next hop must be reachable
- Advertising router perform AS-prepending
- An AS path set is included in your router.
- We are performing calculations to find the fastest way to get somewhere inside an AS
- AS path ensure loop-free topology
Directly Attached Peers
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Going from a physical interfcae to another physical interface
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eBGP packets use a TTL of 1
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eBGP multihop feature extend this
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BGP metrics are often set on neighbor basis
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No manual neighbor discovery
- It is hard-coded
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Authentication supported
/CAP/Network+/Visual%20Aids/Pasted%20image%2020250326131859.png)
eBGP Multihop
/CAP/Network+/Visual%20Aids/Pasted%20image%2020250326132046.png)
- TTL > 1
AS Path Prepending
/CAP/Network+/Visual%20Aids/Pasted%20image%2020250326132146.png)
/CAP/Network+/Visual%20Aids/Pasted%20image%2020250326132322.png)
BGP Looking Glass
- Visit www.bgp4.as
- Type 1 Looking glass = Web Interface
- Type 2 looking glass = CLI Interface
/CAP/Network+/Visual%20Aids/Pasted%20image%2020250326132421.png)
- Run:
show ip bgp summary