BGP Multihop-Network Engineer/Interview Question скачать в хорошем качестве

BGP Multihop-Network Engineer/Interview Question

#BGP #EBGP-Multiho #TTL Value #networkengineers #ospf #trending -: EBGP Multi Hop:- What is eBGP Multihop? By default, eBGP neighbors must be directly connected. • eBGP uses TTL = 1 • So the BGP packet can reach only one hop eBGP Multihop allows BGP neighbors to form a session across multiple hops (routers) by increasing the TTL value. What is TTL = Time To Live TTL is a number in an IP packet that tells the network how many hops (routers) the packet is allowed to pass through before it is discarded. Why TTL Exists? TTL exists to prevent infinite loops. Without TTL: • A packet stuck in a routing loop would circulate forever • That would waste bandwidth and CPU Why do we need eBGP Multihop? eBGP multihop is used when BGP neighbors are not directly connected, for example: • Loopback-to-loopback BGP peering • ISP core routers peering via intermediate routers • MPLS / IGP-based transport • Route reflector / security designs Without multihop → BGP session will never come up. How does eBGP Multihop work? Allow BGP packets to travel more than 1 hop, This is done by increasing the TTL value 3. Security Consideration More exposure to unwanted peers Best practice: use • MD5 authentication • Prefix filters • TTL security (GTSM) Q: Why do we use eBGP multihop with loopback addresses? A: Loopbacks are not directly connected. eBGP default TTL is 1, so multihop is required to allow BGP packets to reach the remote loopback.