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12 votes
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Why does the MTU need to match on interior link state routing protocols like EIGRP and OSPF?

Pete said: I can't think of a situation where you would need this. I just wanted to know what the logic was that makes this an explicit check in these routing protocols. Short answer Routing ...
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10 votes
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Why does EIGRP aim to be loop free?

All routing protocols try to avoid a loop topology. If there is a routing loop, data is not getting to the destination. If the path from source to destination is A -> B -> C -> D, but there is a ...
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9 votes
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Why do summary routes get a low Administrative Distance?

Since the summarized route means that a router advertising it has knowledge of the individual routes within the summarized prefix, it is more trustworthy than the same (summarized) prefix being ...
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6 votes
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How to find EIGRP Neighbor located on other Switch?

Your AS numbers need to match. Change either switch2 to router eigrp 1 or change switch1 to router eigrp 2 and reimplement the routing configuration on the device that is changed.
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6 votes

How to stop a connected network from being advertised in eigrp?

You sound like you are looking for distribute-list. Have a look here for the command reference http://www.cisco.com/c/en/us/td/docs/ios/12_2/iproute/command/reference/fiprrp_r/1rfeigrp.html#wp1030208 ...
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6 votes
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Why is no subnet mask required in EIGRP for classful networks?

By default EIGRP uses a classful network, meaning that it assumes that an address in the class A range with have an 8-bit subnet mask. There is no automatic process of checking other than the ...
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6 votes
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Why can't I ping in this situation?

You have the 10.0.0.0/8 and 172.16.0.0/16 networks defined on both the middle and right routers. Using auto-summary on both makes each think they own those whole summarized networks, so they will not ...
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6 votes

Why do summary routes get a low Administrative Distance?

The AD of the EIGRP summary route is 5 only on the router that has the summary route configured. When the summary is advertised to other routers it has an AD of 90. The reason for the low AD is to ...
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5 votes

Why does the MTU need to match on interior link state routing protocols like EIGRP and OSPF?

According to the OSPF RFC 2328 (10.6): If the Interface MTU field in the Database Description packet indicates an IP datagram size that is larger than the router can accept on the receiving ...
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  • 538
5 votes
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EIGRP to iBGP metric calculation

Since Cisco controls the EIGRP spec, they automatically provide additional information to BGP when EIGRP is advertised/redistributed into an MPLS VPN. This excerpt from Cisco's MPLS VPN support for ...
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5 votes
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How exactly does "bandwidth" in the Cisco IOS affect network performance?

It's a little complex, and also platform specific in some cases. The most general answer is that the bandwidth statement is used as an input to the EIGRP routing protocol. There are also cases where ...
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  • 555
5 votes

How to stop a connected network from being advertised in eigrp?

Create network statements with subnet masks for each interface you do want to advertise and exclude the interface you don't want to advertise. For example, if you have int gi 1/1 ip address 10.1.1.1 ...
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5 votes
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RIP V2 multicasting looks as broadcasting at IP add 224.0.0.9

224.0.0.9 is a protocol standard multicast address, meaning that it is reserved for all RIPv2 speaking routers. This reduces unnecessary overhead, and only speaks to RIPv2 routers, instead of a full ...
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5 votes
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What is the purpose of EIGRP stubs?

There are philosophical differences in the design of OSPF and EIGRP and they are reflected in the protocol operation. For example, OSPF relies on a strict hierarchy/star topology to prevent loops. ...
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5 votes
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EIGRP metric explanation

EIGRP Metric Formula The EIGRP Metric is a combination of a measure of the entire path's cumulative delay, and the minimum bandwidth across the entire path. The delay value is value assigned to each '...
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5 votes
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How do OSPF and EIGRP deal with 2 exactly same routes?

Will ospf and eigrp share the 10 network on the right to their neighbors? As per my understanding link state protocols like ospf do so while eigrp being a distance vector protocol will share ...
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5 votes
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EIGRP failover - how do i verify it happened?

There is a command made for such checking. Use: show ip eigrp events
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5 votes
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No passive-interface error

You have to put your interfaces into vrf 4. interface fa 2/0 ip vrf forwarding 4 An interface can only be in one vrf. Otherwise, how would the router know which interface to use? If you don't ...
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5 votes
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Why does EIGRP have lower Administrative distance than OSPF?

That is because Cisco determines the AD used by its devices, and EIGRP is a Cisco protocol, so Cisco decided to make EIGRP have a lower AD than other protocols. Each vendor determines the relative ...
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5 votes

Ramifications of turning off Spanning Tree for EIGRP network?

Spanning-tree is a loop detection / prevention mechanism. As such, it has nothing to do with EIGRP. Unless you have loops, or parallel layer-2 links in the network, STP isn't doing anything for you. ...
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4 votes

Why I cant Ping An Address across my a routed link

If you are talking about L3 interfaces and EIGRP, we must assume this: Network1: Switch1 - Firewall Network2: Switch2 - Switch1 First. You need to set-up on your firewall EIGRP(on the way to LEARN ...
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4 votes
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How does EIGRP determine the path to far away destinations?

There seems to be a confusion here : in a distance-vector routing protocol, the routers don't just get routes to their neighbors (which would be trivial in most cases) they get their neighbor's full ...
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4 votes
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Choosing a routing protocol

To choose a routing protocol you should consider these topics: Configuration: How easy is to configure and troubleshoot the protocol. Efficiency: How fast it converges? How much bandwith it uses? ...
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4 votes

EIGRP failover - how do i verify it happened?

Yes, you can confirm that. Once hold-time expires, the former feasible successor route immediately becomes the successor route and is installed in routing table. I do not think we have a log message ...
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  • 3,744
4 votes

No passive-interface error

From your configs, interface FastEthernet2/0 is not part of vrf 4 that your EIGRP is configured for oneither of your routers. Try adding your interface to the vrf with the following. interface ...
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  • 536
4 votes
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Filter routes based on interface

You can specify what routes exactly you want to receive from neighbor on specific interface by using distribute-list option: (conf)# router eigrp 10 (config-router)# distribute-list 50 in Tunnel 3 ...
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4 votes
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EIGRP authentication on GRE tunnel interface?

Yes, you can do that. Below is an example: Router-A# ! key chain Netlab key 13 key-string Netlabbuilder ! interface Tunnel1 description Site-B ip address 10.99.99.1 255.255.255.252 ip mtu 1400 ...
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4 votes
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EIGRP Auto-summary

Auto-summary summarizes network advertisements based on classful boundaries. Since classful addressing has been obsolete since before you were born, it's good practice to disable it.
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4 votes
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Ramifications of turning off Spanning Tree for EIGRP network?

switch that has elected itself You should never leave the root bridge to chance. If the current root switch goes offline or is rebooted your spanning tree needs to reconverge, causing temporary ...
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