[bdNOG] BGP configuration issue in Caching Solution System

Nurul Islam Roman nurul at apnic.net
Fri Nov 22 03:02:00 BDT 2013

Consider an external "Host (Source IP)" trying to reach your "Caching Control Server (Destination IP)" through L3 Switch. Packet comes all the way up to RouterA. Route table lookup done. What next hope found? BGP Caching Control Server? How the next hop is reachable? Via IGP (OSPF)? Packet comes to L3 switch. Again Routing lookup. Is destination (Caching control server) prefix available on L3 switch? What next hop found? Is it reachable via IGP? Packet comes to Caching control server.

Now return path. External host IP will be destination address. Is there any match in (Caching control server)? What is next hop? It has to be ROUTER A loopback (need next hop self on RouterA) and need to be reachable via IGP. Packet comes to L3 switch. Routing lookup. Any match to external host network on L3 switch routing table? Probably no. Black hole in your return path. You have already disable BGP sync rule. Need iBGP full mesh peering (also with L3 switch).



From: Mirza Rakib <mmrakib at gmail.com<mailto:mmrakib at gmail.com>>
Date: Friday, 22 November 2013 1:41 AM
To: "nog at bdnog.org<mailto:nog at bdnog.org>" <nog at bdnog.org<mailto:nog at bdnog.org>>
Subject: [bdNOG] BGP configuration issue in Caching Solution System

Hi Team,

I am facing an issue to configure internal BGP (iBGP) where a L3 switch exist in between Router and another Caching Solution Server. The architecture like:

Router-A(BGP, AS45245)----L3 Switch(3 different VALNs: VLAN10, VLAN20 and VLAN30)-------BGP Caching Control Server( AS45245, VLAN10)

BGP formed but there is routing issue. We can reach Router-A to all Servers in differnet VLANs and  vice versa but cannot reach outside and also from outside to servers are not reachable. We are getting some sites IP in BGP Caching Control Server bgp table. However we not reacing there, we got loop or stack at L3 switch, whenever we trace.

Mirza Rakib

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