BGP OSPF Questions: Difference between revisions
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= EIGRP =
* EIGRP runs on ip protocol 88
* Eigrp is hybrid protocol and has some properties of distance vector and some link state.
* Distance vector - Only knows what its directly connected neibors are advertizing and link state because it form adjancies .
* Inorder to form adjancency EIGRP AS no should be same between neihbours.
* EIGRP Multicast adress - 224.0.0.10
* EIGRP is like bgp will only advertize the route which is going to install in routing table.
* EIGRP classes protocol does automatic summary by default, so we need to disable the automatic summarisation (no auto summary)
* EIGRP does spilt horizon, in case of DMVPN we need to disable the split horizon so that routes learned on tunnel interface through one spoke need to advertize to other spoke through same tunnel interface.
* Passive interface command works silghtly different in EIGRP, it stops sending multicast/unicast hello to nei thus prevent forming adjancies.
* Issuing a neighbour statment in eigrp on a link means it stops listen to mutlicast address so we need to specify the neighbour mannuly to other side to form adjancies.
* Timers in EIGRP is not nessescary to match to form adjancey.
* EIGRP - Metric calculation by bandwidth, delay, relibilty, load MTU.
* Bandwidth is scaled as minimum bandwidth and total delay, highest load, lowest reliablilty while calculating composite metric.
* Feasible distance is best metric along the path and its successor metric .
* EIGRP - FD-is best metric along the path to desination router including metric to reach the neibor
* Advertised distance -total metric along the path advertized by up stream router.
* A router is feasible successor if AD<FD of successor
* FD is used for loop avoidance. spilt horizonrule -never advertized the route on the interface on which it is learned.
* Feasible succesors are only candidates for unequal path load balancing.
* Load balancing is done in EIGRP though unequal cost paths through variance multiplier.
* EIGRP is only routing protocol that supports load balancing across unequal path unlike like rip, ospf, Isis.
* FD <= FSx variance (FD) then the path is choosen for unequal cost load balancing.
* EIGRP traffic eng. could be easily achieved by modify the delay value instead of bandwidth.
* EIGRP command
sh ip eigrp nei
sh ip eigrp nei de
sh ip eigrp topology
sh ip eigrp route
* Equal cost load balancing the traffic is distributed based on CEF. To turn off cef on interface do (no ip route-cache)
* SIA -Stuck in active, If router receive a queries for destination network it taking too much time to respond be because of network flap or some network condition occur route is considered in SIA state.
* We can tune the amount of time router should wait before putting route in SIA state by timers acive-time command
* To check which routers have not replied with queries issue sh ip eigrp topolgy, router denoted by R meaning waiting for replies.
* EIGRP perpforms auto summarization for a n/w when crossing a major n/w boundary
* Split horizon should only be disabled on a hub site in a hub-and-spoke network:
no ip split-horizon eigrp x
* EIGRP router id helps in loop prevention for external routes which says if I gets the routes with orignator that is equal to my router id then I will discard the routes.
* EIGRP provides faster convergnece as it doesnot need to run dual algo in case if there is feasible successor for the path, else if router do not have route it will send the query to its neibour router which will further progates the query to there neibours if the router does not recive the reply from the neibour before the timer expires it will mark this route in Stuck in active state and reset its neibour relationship if all its query are not answered with time time period.
* While in OSPF if the primary path goes down, it need to send the LSA and SPF algo is run again.
* dcesor in mind.
* There is ways to bound the query domain You can do in either of 2 ways or both
1) Using Summary routes -ip summary-address eigrp 'as' [network] [mask] [ad]
If RouterA sends a query message to RouterB and summarization is in use, RouterB will only have a summary router in its EIGRP topology table not the exact prefix match of the query and will therefore send a network unknown response back to routerA. This stops the query process immediately at RouterB, only one hop away.
2) Using Stub -
router eigrp 1
eigrp stub 'arguments'
The default arguments are connected and summary this means it will advertised connected and summary routes only.
A router will inform it neighbor of it stub status during the neighbor adjacency
forming
Stub routers tell their neighbors
3. filtering the prefix
please note Eigrp neighbor router will propagate query received from neighbor router only if it has the extact match for the route ints topology table, if router doesnot have exact route in toplogy table it will send the reply with route unknow to its neighbor and further query will not be propagated .
4.Different AS domains
Different EIGRP AS numbers. EIGRP processes run independently from each other, and queries from one system don\92t leak into another. However, if redistribution is configured between two processes a behavior similar to query leaking is observed.
* Both IGRP and EIGRP use an Autonomous System (AS) number and only routers using the same AS number can exchange routing information using that protocol. When routing information is propagated between IGRP and EIGRP, redistribution has to be manually configured because IGRP and EIGRP use different AS numbers. However, redistribution occurs automatically when both IGRP and EIGRP use the same AS number
= MPLS =
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