Routing Protocol RIP , EIGRP, OSPF, BGP

OSPF

Init hello

Two way state – all ospf config match

LB database list exchange

DD packet, ospf description,

BDR copy DR routing so it can take over

LSU is the packet and LSA is the structure LSDB take in

Issue with large OSPF design

1. Too much CPU to run SPF algorith in topology
2. Requires more meomry in ram
3. A single interface status change, anyhwere in the internetwork forces every router to run spf again.

Advantage of Area design

1. Smaller per area LSDB requires less memory.
2. Routers require fewer CPU cycles to process the smaller per area LSDB with the SPF algorithm, reducing CPU overhead and improving convergence time.
3. Changes in the network ( for example links failing and recovering) require SPF calculation only on routers connected to the area where the link changed state, reducing the number of routers that must rerun SPF.
4. Less information must be advertised between areas, reducing the bandwidth required to send LSAs.

Ospf config

Router ospf 1 (process-id can be 1-65535)

Router-id 1.1.1.1 ( staticlly configure router-id or loopback with highest numeric ip address, or other highest ip address from other interface)

Network 10.0.0.0 0.255.255.255 area 0

Interface S0/0/0

Ip address 10.1.1.1 255.255.255.0

Show ip ospf neighbor- neighbor id, state, address, interface

Show ip ospf database – area, neighbor link id, age,

Show ip ospf interface- passive interface

Show ip ospf interfaces brief – ospf enabled interface, ip, area, cost, state

Show ip route – ospf routes in O

Show ip protocol – routing protocol, routing id, routing network, neighbor router

Passive-interface <interface >

1. Quit sedding OSPF hellos on the itnerface
2. Ignor receiving hellow in the interface
3. Do not form neighbor relationship over the interface

Default route

Default-information originate

Default-information originate always

Cost

Auto-cost reference-bandwidth <mbps>

Load Balancing

1. Maximum-paths <number>
   1. Under router ospf , Max hop to destination

Interface configuration

1. No network <netowrk id> area <area id>
2. Ip ospf <process-id> area <area id>
   1. On to the interface

Hello message every 10 seconds

OSPF ipv6

1. OSPF2 vs OSPF3
   1. Similarity
      1. Both are link-state protocol
      2. Both use the same area design concepts and design terms
      3. Both reuire that the routing protocol be enabled on an interface.
      4. Once enabled on an interface, both then attempt to discover neighbors connecteed to the data link connected to an interface.
      5. Both perform a check of certain setting before rouers become neighbors
      6. After two router becom neighbors, both OSPFv2 and 3 proceed by exchanging the contents of their LSDB – the LSA and describe the network topology, between the two neighbors.
      7. After all the LSAs have been exchanged, both OSPFv2 and v3 use the shortest path first (SPF) algorithm to calculate the best route to each subnet.
      8. Both use the same metric concept, based on the interface cost of each interface, with the same default cost values.
      9. Both use LSAs to describe the topology, with some differences in how LSAs work.
2. Configure
   1. Int gi 0/0
      1. Ipv6 address xxxxx
      2. Ipv6 ospf 2 area 23
      3. # Ipv6 ospf cost x
      4. # bandwidth [speed]
      5. # Auto-cost reference-bandwidth
      6. # maximum-paths [number]
   2. Int s0
      1. Ipv6 ospf 2 area 23
      2. Ipv6 address xxxx
   3. Ipv6 router ospf 2
      1. Router-id 2.2.2.2
      2. # passive-interface gi0/1
   4. Default-information originate (advertise default route)
3. Troubleshoot

EIGRP

1. Uses update messages from neighbors 10 seconds
   1. Full updae means that a router advertised all its routes using one or more rip update messages.
   2. Periodic means rhe router sends message short timed period
2. Split horizon is a DV feature that tells the reouting protocol to not advertisse some routers in an update sent out the same inteerface as the outgoing interface.
3. Route poisoning advertising a failed or deleted route with a metric infinity
   1. Router receive the advertisement for subnet with inifnity, it decides to mark route as unusable and delete later or removes the route.
4. Hello timer 5 sec
5. Hold timer 15 sec

1. For a neighbor relationship
   1. Pass authentificaiton
   2. ASN configured
   3. Network subnet
2. Uses RTP instead of udp or tcp
3. For metric , eigrp uses bandwidth and delay in default
   1. Support interface load
   2. Reliability
   3. Mtu
4. Find delay in show interface and bandwith then ue show ip eigrp topogy for eigrp updates
5. Feasible distance (FD) the local router;s composite metric of the best route to reach a subnet, as calculated on the local router
6. Reported distance (RD) the next hop router best composite metric for that same subnet
7. RD and FD determine the feasable successor route
   1. Feasable successor are alternate immediately usable routes
8. Best metric route is called successor
9. ((10^7/bandwith)+delay)*256
10. Diffusing Update Algorithm(DUAL) sends queriess looking for a loop free route to the sbnet and when the new route is found DUAL adds it to the routing table.
    1. Eigrp query is sent from the router with no feasible successor route and the router receives a eigrp reply message and add to the routing table..

Vriance, a eigrp setting allowing routes whose metrics are relatively close in value to be considered equal. Multiplies by the current FD.

Debug eigrp packets

Debug ospf hello

EIGRP IPv6

1. Config
   1. Ipv6 unicast-routing
   2. Ipv6 router eigrp 1
      1. Eigrp router-id 1.1.1.1
      2. # maximum-paths x
      3. # variance 4
   3. Int gi0/0
      1. Ipv6 address 2001:db8:1:1::1/64
      2. Ipv6 eigrp 1
   4. Int s0
      1. Ipv6 address xxxxxxx
      2. Ipv6 eigrp 1
   5. Int s1
      1. Ipv6 address xxxxxxxxx
      2. Ipv6 eigrp1
2. Troubleshooting

BGP

1. Uses path attributes insead of metrics
2. Uses process called best path selection to choose the best route.
3. Internet edge PE to CE
4. Predefine neighbors with
   1. Neighbor <ip> remote-as <asn>
5. Advertise about prefixes that have been added to the BGP table using
   1. The BGP network command
   2. Route redistribution
   3. By learning prefixes from a neighbor
6. Use TCP port 179
7. BGP peer send update messags which hold prefix/length(NLRI) informaiton and associated path attributes (PA).
8. Config
   1. Router bgp 1
      1. Neighbor <ip> remote-as <asn>
9. Show tcp brief
   1. Show tcp connection
10. Show ip bgp summary
    1. Show as number, router id, neighbor ip and asn state

1. Neighbor <ip> shutdown
   1. Administratively disabling neighbor
2. Network <ip> mask <subnet>
   1. Inject the network to the bgp routing table
   2. Show ip route <ip> <subnet> longer-prefix