A. http://www.cisco.com/web/about/security/intelligence/spd.html see this link it has very useful info, let me know for any follow up question/put it on the community.
A: BGP is open standard, scalable, and available attributes helps tweak incoming and outgoing traffic. In IGP you can influence egress routes but no knob to influence neighbor's decision.
A: You can use VIRL.
A: Yes, BGP uses tcp port 179 to communicate with neighbor and 3 way handshake is underline mechanism.
A: BGP supports multiprotocol.. it means you can redistribute eigrp/rip etc into bgp, so the command ipv4 unicast prepares the router for this capability
Refer this link for more info, -http://www.cisco.com/c/en/us/td/docs/ios/iproute_bgp/command/reference/irg_book/irg_bgp1.html#wp1110597
A: Local preference helps determine which path to choose for exiting should you have multi path available.. higher the better and default value is 100.
A: 1) http://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/116377-troubleshoot-bgp-mtu.html 2) debug ip bgp 3) ensure route to neighbor is not flapping 4) layer 1 issue/ match config with provider 5) high cpu verification are good starting
A: Yes, and here is good doc for the same http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_bfd/configuration/15-mt/irb-15-mt-book/irb-bi-fwd-det.html#GUID-228FE545-B864-4819-ABDA-BC915874384E
A: ISP can distinguish routes from various customers and apply policies accordingly, its easy way to recognize bunch of routes collectively.. so send-community is used to send that info out for provider to recognize it and take action if any.
A: For bgp : show ip bgp neigh x.x.x.x receive routes and show ip bgp neigh x.x.x.x adv routes. for ospf you have to ensure you are advertising desired networks and they are in ospf database "show ip ospf database"
A: You can use route-map to set as path prepend or modify MED value (lower the better) to influence routing. AS path prepend can be used to add extra AS path on less preferred path as shorter is preferred.
A: http://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/13753-25.html - this is how path selection works.
A: Use of MED, its kind of metrics like we have in IGP, its again used as an attribute and used to influence traffic e between different AS.
A: Yes, we can.
A: Router id really helps kind of making uniquely identify particular information while at the same time it has some information that is exchanged between the routers. It’s a good practice to configure loop back addresses as router id and that has been recommended also so that you know how to reach particular router within the network. Apart from that it’s not really required for forming any kind of BGP neighboring.
A: Prefix is something that is advertised to a peer. It becomes the route when it is selected as the best and installed in the routing table.
A: If you notice the IBGP configuration we did the peering. When you are using the peering via loopback address, you need to have the loopback reachability; these IBGP provides the loopback to loopback reachability. You can also have static routes but if you look at within a autonomous system environment having 100s of routers, it is not really a scalable way to run a static route everywhere. Better option is to configure IBGP within those 100 routers and have reachability to any loopbacks across the network. You can form IBGP connection between any Router A / Router C/ Router G which are sitting 20 hops away and not direction is required.
A: "show ip bgp neighbors [ip-address] routes" to look at the bgp routes coming from BGP peer.
A: Why it is recommended is that say if you are not using and say you are using a different address family using vrs, it becomes difficult if you are using vrs to identify which ip is router id unless you are describing in the description. Better option is using a router id you can identify the node properly and it makes really simpler to manage your network.