1.  Create the keys in the keychain.

R101(config)#key chain KEYCHAIN
R101(config-keychain)#key 1
R101(config-keychain-key)#key-str
R101(config-keychain-key)#key-string MYKEY

2.  Enable authentication on an interface.

R101(config-if)#ip authentication mode eigrp 1 md5

3.  Associate keychain with EIGRP.

ip authentication key-chain eigrp 1 KEYCHAIN

Aaron Conaway

I like to lean my head to the left, hit it with the palm of my right hand, and document what knowledge falls out.

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You can configure an EIGRP router to filter routes from being advertised or from being accepted.

Objective:  Filter out the route to 10.0.254.1/32 from being advertised to the rest of the network via EIGRP.

ip prefix-list PRE1 deny 10.0.254.1/32
ip prefix-list PRE1 permit 0.0.0.0/0 le 32
!
router eigrp 1
 distribute-list prefix PRE1 out

-- OR --

ip access-list standard ACL1
 deny 10.0.254.1 0.0.0.255
 permit any
!
router eigrp 1
 distribute-list ACL1 out

Aaron Conaway

I like to lean my head to the left, hit it with the palm of my right hand, and document what knowledge falls out.

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One of EIGRP’s big features is the ability to use unequal cost paths for load balancing.  This is done with the variance command.

variance : A multiplier used to calculate which feasible successors can be used as active routes.  The router takes integer and multiplies it by the successor’s feasible distance, and any FS with a an FD less than this new number gets submitted to the routing table manager.

R1(config-router)#variance ?
 <1-128>  Metric variance multiplier

maximum-paths : The maximum number of routes to submit to the route table manager.

R1(config-router)#maximum-paths ?
  <1-32>  Number of paths

traffic-share balanced : The router sends traffic based on a weighted values of the metric so that the lower metrics get more traffic.

R1(config-router)#traffic-share balanced

traffic-share min : Only use the lowest metric route.  This seems kind of pointless to me.

R1(config-router)#traffic-share min

traffic-share min across-interfaces : Use the lowest metric route but use routes out different interfaces if they exist.

R1(config-router)#traffic-share min across-interfaces

Aaron Conaway

I like to lean my head to the left, hit it with the palm of my right hand, and document what knowledge falls out.

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Configuration

There are quite a few differences between EIGRP for IPv6 (yes, that's an official name) and the IPv4 version.  First of all, all IPv6 routing is disabled by default on a Cisco router, so, if you're doing any routing in IPv6, you'll want to enable it or risk smashing your head into the desk trying to figure out what's going on.

Router(config)#ipv6 unicast-routing

Next, let's get to configuring EIGRP for IPv6.  By default, IPv6 routing protocols (all of them?) are EIGRP for IPv6 is shut down like Ethernet interfaces, so we'll have to enable it first.  

Router(config)#ipv6 router eigrp 100
Router(config-rtr)#no shutdown

There's also the issue of the router ID.  In IPv4, EIGRP has an method to figure out its router ID, and EIGRP for IPv6 uses that same method.  The problem is that the router ID is still a 32-bit number, but there aren't any 32-bit address on the router if you're pure IPv6.  A dilemma, eh?  There are two way to get around this, though.  First, you can set a loopback interface with an IPv4 address so that EIGRP will have an address to use.

Router(config)#interface lo0
Router(config-if)#ip address 192.0.2.1 255.255.255.255

You can also statically assign a router ID to EIGRP for IPv6.

Router(config)#ipv6 router eigrp 100
Router(config-rtr)#router-id 192.0.2.1

Either method gets the same result.  Of course, you should be careful that all routers have a unique ID.

So now we need to add some network statements, right?  Actually, there are no network statements in EIGRP for IPv6.  The interfaces themselves are where you configure the networks to be included in the routing protocol.  It's kinda like the way you can use the interfaces to configure OSPFv2.

Router(config)#interface f0/0
Router(config-if)#ipv6 eigrp 100

Of course, we're assuming you already have an IPv6 address on f0/0.

Checking our Work

Let's check to see if everything is working the way we think it should be.  First of all, let's make sure all our interfaces are participating as expected with the show ipv6 eigrp interface command.

Router#sh ipv6 eigrp interfaces
IPv6-EIGRP interfaces for process 100

                        Xmit Queue   Mean   Pacing Time   Multicast    Pending
Interface        Peers  Un/Reliable  SRTT   Un/Reliable   Flow Timer   Routes
Fa0/0              0        0/0         0       0/1            0           0
Fa0/1              1        0/0        23       0/2           50           0

This output looks a lot like the IPv6 version, and we can see both f0/0 and 0/1 are participating.  That looks right, so let's check for EIGRP neighbors with the show ipv6 eigrp neighbor.  I've got another router off of f0/1, so we should see a neighbor adjacency.

Router#sh ipv6 eigrp neighbors
IPv6-EIGRP neighbors for process 100
H   Address                 Interface       Hold Uptime   SRTT   RTO  Q  Seq
                                            (sec)         (ms)       Cnt Num
0   Link-local address:     Fa0/1             13 00:02:40   23   200  0  11
    FE80::C001:14FF:FEB0:1

What the heck is FE80::C001:14FF:FEB0:1??!?!?!  That's not a network we configured!  That's actually the link-local address of the other router off of f0/1.  Perhaps I'll discuss IPv6 addressing some day (when I have a firmer grasp on it), but, for now, I'll just say that it's a special address for hosts to talk to one another on a local network.

Finally, let's check for routes.

R1#show ipv6 route eigrp
IPv6 Routing Table - 6 entries
...
D   2002::/64 [90/307200]
     via FE80::C001:14FF:FEB0:1, FastEthernet0/1

Just like in IPv4, EIGRP for IPv6 routes show up with the route code of "D".  It's looks like we have one route to the 2002::/64 network.  Everything seems to be working!

There are obviously a lot of more features and functions to EIGRP for IPv6, but this should get you started in your studies.  I'm sure I'll expound as time and my CCIE studies progress.

Send any 6to4 tunnels questions my way.

Aaron Conaway

I like to lean my head to the left, hit it with the palm of my right hand, and document what knowledge falls out.

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The config is quite easy and involves my favorite config item in all of Ciscodom – route-maps!  You create a route-map that sets the tag value and apply it to the redistribution.  There are a few ways to skin this cat, but I'll use an outbound distribute-list here.  Here's the config save the basics for getting EIGRP going.

route-map TAGIT permit 100
 set tag 2000
!
router eigrp 1
 redistribute static
 distribute-list route-map TAGIT out
!
ip route 172.16.0.0 255.255.255.0 Null0

If you do a show ip route on one of the other routers, you can see the tag that has been applied.  Check out the last line of the output.

R1#sh ip route 172.16.0.1
Routing entry for 172.16.0.0/24
  Known via "eigrp 1", distance 170, metric 28160
  Tag 2000, type external
  Redistributing via eigrp 1
  Last update from 192.168.0.2 on FastEthernet0/0, 00:00:09 ago
  Routing Descriptor Blocks:
  * 192.168.0.2, from 192.168.0.2, 00:00:09 ago, via FastEthernet0/0
      Route metric is 28160, traffic share count is 1
      Total delay is 100 microseconds, minimum bandwidth is 100000 Kbit
      Reliability 255/255, minimum MTU 1500 bytes
      Loading 1/255, Hops 1
      Route tag 2000

Remember that you can only tag routes external to the AS.  That means you can't have a router tag all the internal routes (which may be a cool thing to be able to do).  You can, however, tag any route that is redistributed – including another EIGRP AS. 

Tags are also used in OSPF and BGP.  Our MPLS provider actually tags the routes they distribute to us with their BGP AS number.

Send any infinite-hop routes questions my way.

Aaron Conaway

I like to lean my head to the left, hit it with the palm of my right hand, and document what knowledge falls out.

Website - More Posts

Study Questions

• I’ve got IGRP and EIGRP both configured with the same AS number.  What’s special about this configuration?

If both use the same AS number, then they automatically redistribute their routes into each other without using the redistribute command.

• When redistributing one IGP into another, where’s a good place to filter routes?

There’s no one good place, but at the router(s) that’s doing the redistribution is a good start.  There’s no need to send an IGP a bunch of routes it doesn’t need.

• When redistributing one IGP into another, where’s a good place to summarize routes?

There’s no one good place, but that may be best done at the router just inside the redistributing router.  If the redistributing router only sees the summary route, that’s what it will pass to the other IGP.

• What’s the default metric of RIP?

That’s infinity, so it’s unreachable with an explicit metric.

• I’ve redistributed OSPF into RIP, but I don’t see my subnets there.  What gives?

RIP automatically summarized routes, so look for summaries instead of specific subnets.

• How can you limit the number of routes redistributed into EIGRP or OSPF?

Use the redistribute maximum-prefix X directive under the routing protocol, where X is the maximum number of routes.

• What are the metrics of connected routes when redistributed into EIGRP?

Those routes take the metric of the associated interface instead of using the metric you gave to the redistribution.  [This seems fishy at best.  Can anyone help clarify, please?]

• I have 845734928 interfaces on my router, but I only want to use 3 of them for EIGRP and only want to configure a single network statement.  What’s the easiest way to do that?

Set all the interfaces as passive with the passive-interface default router subcommand.  Next, make all your interesting interfaces non-passive with the no passive-interface X subcommand.  Now you can configure network 0.0.0.0 255.255.255.255 to match all the interfaces, but only the interesting interfaces will participate.

• What is the term for the rank of trustworthiness a routing protocol provides?

Administrative distance

• How can I change the AD of external EIGRP routes to 201 while keeping the default AD for internal EIGRP routes?

Router1(config-router)#distance eigrp 90 201
You have to set both, so you’ll have to remember that EIGRP has an AD of 90 for internal routes by default.

• How can I change the AD of OSPF routes to 192.168.0.0/24 to 202?

Router1(config)#access-list 88 permit 192.168.0.0 0.0.0.255
Router1(config)#router ospf X
Router1(config)#distance 202 0.0.0.0 255.255.255.255 88

• Is it possible to set the AD of different OSPF routes types like intra-area and interarea?

Yes.  You can give it the old distance ospf inter-area X to change the AD.  It also works for intra-area and external routes.

• Is it possible to set the AD of an external OSPF route to 192.168.100.0/24 to 202 without changing the others?

I would have though you could use a route-map for that, but I can’t find a proper set command in a route-map.  [A little help, please.]

Aaron Conaway

I like to lean my head to the left, hit it with the palm of my right hand, and document what knowledge falls out.

Website - More Posts

Study Questions

• What three things are needed to be able to redistribute one routing protocol into another?

1. One or more links into each routing protocol
2. A proper, working config for each protocol
3. The addition of the redistribute command to one or more of the protocols

• You just configured OSPF to redistribute EIGRP routes, but EIGRP, with the network statement of network 0.0.0.0 0.0.0.0, is configured with a passive interface.  Does this interface’s connected network get redistributed?

Yes, it does.  Even if it’s not participating in routing, it’s still an interface that EIGRP is configured to use, so it goes along for a ride on the redistribution train.

• Name three ways to set the metric of redistributed routes in EIGRP.

1.  default-metric …
2.  redistribute X metric …
3.  redistribute X route-map …

• How can I set the metric for all OSPF routes redistributed into EIGRP?

Use the redistribute ospf X metric command.

• You are redistributing OSPF into EIGRP and want to set the metric of one particular route to another set of metric values (BW, delay, etc.).  How do you do that?

Use a route-map to match the single route and to set the new values.

• Routes from what routing protocol need a metric set when redistributing into EIGRP?  Routes from what protocols don’t?

Routes from another EIGRP instance have their metrics copied over; all others need to have it set.

• What’s the default metric of a BGP route when redistributed into OSPF?  EIGRP?

BGP has a metric of 1 in OSPF.  There is not default metric in EIGRP without some configuration.

• You left out the subnet keyword when redistributing EIGRP into OSPF.  What is the result?

Only classful routes will be redistributed and only if EIGRP has a classful route to redistribute.

• You left out the subnet keyword when redistributing OSPF into EIGRP .  What is the result?

There is no subnet keyword for redistribution under EIGRP.

• Routes from what routing protocol need a metric set when redistributing into OSPF?  Routes from what protocols don’t?

OSPF set metrics automatically.  If the route came from another OSPF process, the metric is copied over.  If the route came from BGP, the metric is set to 1; if it came from any other routing protocol, the metric is set to 20.

• What are three ways to manipulate the metric of redistributed routes in OSPF?

1.  default-metric …
2.  redistribute X metric …
3.  redistribute X route-map …

• My ASBR is advertising static routes into area 0, but I’m not seeing any type-5 LSAs in area 1.  What’s gives?

Assuming everything else is configured correctly and no filtering is done, area 1 is probably a stub area of some kind.

• My ASBR is advertising static routes into area 1, but I’m not seeing any type-5 LSAs in that area.  What gives?

Area 1 is probably an NSSA or totally NSSA area, so any external routes are flooded as type-7s – note type-5s.

• If I look at the OSPF database on my router, I see that a whole bunch of type-5 LSAs advertised from the router with the ID of 1.1.1.1.  What does that say about that router?

Among other things, that router is an ASBR and is redistributing external routes into that area.

• I see several routes in the OSPF database with a cost of 20.  What metric type are those routes?

More likely than not, they are type-2 routes (O E2).

• I have two type-5 LSAs for the same network through two different ABRs; both are of the type-2 metric.  How does the router decide which one to use?

Since both routes are E2, they will have a metric of 20 (unless manipulated somehow), so looking at the intra-area cost results in a tie.  The router will then look at the type-4 LSAs which contain the cost from the ABR to the ASBR.  Since each ABR floods these type-4s, the router knows which ABR is closer to the ASBR advertising the route.  The lower metric in the type-4 LSAs wins.

• I have two type-5 LSAs for the same network through two different ABRs; both are of the type-1 metric.  How does the router decide which one to use?

Since both routes are E1, the costs to the ABR are first compared since they may be different.  If tied, the type-4 LSA’s cost to the ASBR is compared.  If still tied, the external (type-5 LSAs) cost is compared.

• I have two type-5 LSAs for the same network through two different ABRs; one is type-1 and the other is type-2 ?  How does the router decide which one to use?

E1 routes are always preferred over E2 routes.

• Why can’t you redistribute static routes into a stubby network?  How can you make it work?

Stub networks do not flood type-5 LSAs, so the routes cannot be advertised into the area.  You can change it to a regular area to make it work.  You can also make it an NSSA or totally NSSA area.

• How do OSPF routes that come from type-7 LSAs appear in the routing table?

They appear as “O N1″ or “O N2″ depending on the metric type.

Aaron Conaway

I like to lean my head to the left, hit it with the palm of my right hand, and document what knowledge falls out.

Website - More Posts

• Why would anyone develop a version of RIP that supports IPv6?

I have no idea.  Boredom, maybe.  Whatever the case, it works just like RIPv2, which is pretty scary.

• In EIGRP for IPv4, there are several requirements for two routers to neighbor up.  Which of those is not true for EIGRP for IPv6?

The two routers don’t need to be in the same subnet.  The concept of the link local address takes care of that need since neighbors always share a common medium like an Ethernet segment or a serial link.

• I configured EIGRP for IPv6 on my completely IPv6 router, but it’s not working.  Nothing happens.  What’s going on?

For one, you have to do a no shutdown as an EIGRP subcommand; by default, EIGRP for IPv6 is in a shutdown state.  Another reason could be that a router ID hasn’t been set; EIGRP for IPv6 still uses the IPv4 addresses to establish a router ID, so you may have to set one manually.

• I tried to configure EIGRP for IPv6 with the network statements, but it’s not taking the command.  What gives?

You actually configure EIGRP for IPv6 (and RIPng and OSPFv3) the “new way” by using the interfaces.  Try doing a ipv6 eigrp X as an interface subcommand.

• When redistributing one IPv6 IGP into another, what kinds of routes will and won’t be redistributed?

Only routes discovered via the original IGP will be redistributed.  Connected routes, even the ones configured in the original IGP, won’t be redistributed.  Link local addresses and local routes will also NOT be redistributed.

• Show me a simple RIPng config.

R1(config)#ipv6 router rip PROC-NAME
R1(config-rtr)#int f0/0
R1(config-if)#ipv6 rip PROC-NAME enable

• Show me a simple EIGRP for IPv6 config.

R1(config)#ipv6 router eigrp 8
R1(config-rtr)#router-id 1.1.1.1
R1(config-rtr)#no shutdown
R1(config-rtr)#int f0/0
R1(config-if)#ipv6 eigrp 8

• Show me a simple OSPFv3 config.

R1(config)#ipv6 router ospf 4
R1(config-rtr)#router-id 1.1.1.1
R1(config-rtr)#int f0/0
R1(config-if)#ipv6 ospf 4 area 0

• How do you include connected routes when redistributing one IGP into another in IPv6?

Use the include-connected directive in the redistribution command.

• In EIGRP for IPv6, what address shows up as the next hop in the routing table?

The link local address of the advertising router.

What Command Was That

What command is used to…

• …show all the IPv6 routes?

show ipv6 route

• …shows the status of OSPFv3 neighbors?

show ipv6 ospf neighbor

• …shows the status of RIPng neighbors?

There is none; RIPng doesn’t have neighbors.

• …shows a route to a specific prefix?

show ipv6 route prefix::/length

Aaron Conaway

I like to lean my head to the left, hit it with the palm of my right hand, and document what knowledge falls out.

Website - More Posts

Study Notes

• When a router redistributes from one routing protocol to another, where does the router get the list of routes to redistribute?

From the routing table.  Only IGP A’s routes (not topology or successors) are redistributed into IGP B’s domain.

• What are two methods of filtering redistributed routes?

Use a route-map in the redistribute line or a distribute-list.

• Of the two methods for filtering, which one has more options?

The route-map method has more options.  You can match on all sorts of stuff, including an ACL or interface, and filter based on that.

• How does using distribute-lists differ between OSPF and EIGRP?

In EIGRP, distribute-lists are used to keep a route from being propagated.  In OSPF, they’re used to keep routes from reaching the routing table.  The effect is basically the same, but the cause is very different.

• How do I redistribute an EIGRP into OSPF as an E1?

You can set that that in the redistribute command.  You can also match a route-map and set the metric-type there.

• What is a big pitfall of having two routes mutually redistribute the same two IGPs?

A router could redistribute IGP A’s routes into IGP B where the second router redistributes them back into IGP A.  Potentially, either router could choose very long routes to get to a destination based on the different ADs and metrics of the IGPs.

• How can I keep this domain loop from happening?

Set the metrics of the redistributed routes so that the originating IGP has the preferred path
Set the AD on the redistributed routes so that the  originating IGP has the preferred path
Manually filter routes so one IGP isn’t presented with its own routes
Use route-tags to mark redistributed routes to filter or manipulate later

• How do you change the metrics of the routes?

You can use the redistribute command to set the metrics.  You can also use route-maps to match routes or tags and set the metric.

• How do I change the AD of the routes?

You can use the distance subcommand to set the AD on the whole domain or from a specific originating (or redistributing) router.

• How do I change the AD for route from 1.1.1.1 to 201?

R1(config-router)#distance 201 1.1.1.1 0.0.0.0

• How do I set a route-tag?

Use a route-map to match the routes you want to tag, and use the set tag directive.

• How does using EIGRP as one of my IGPs help me with mutual redistribution on multiple routers?

EIGRP actually has two ADs – 90 for internal and 170 for external routes.  If a route is redistributed into EIGRP, it will have an AD of 170, so it will be less preferred than interal EIGRP, OSPF, or RIP routes.  Unless you’re using internal BGP or custom ADs, this will keep a looping route out of the routing table and, thus, from being redistributed.

• How does using OSPF as one of my IGPs help me with mutual redistribution on multiple routers?

You may be able to use the metric-types to do some filtering, but the cool AD thing is for EIGRP only.  Since external OSPF routes have an AD of 110 just like internal routes, you can’t rely on AD to keep the looping routes out like you can with EIGRP.

• How does using RIP as one of my IGPs help me with mutual redistribution on multiple routers?

RIP never helped anyone with anything.  Just convert your RIP routers to EIGRP and be much happier.

• What’s a quick way to have OSPF set all external routes to an AD of 201?

R1(config-router)#distance ospf external 201

• What happens if I have OSPF redistributing into EIGRP redistributing into RIP (all mutually)?

You may wind up with a VERY long path without some intervention.  You’ll need to do some filtering on the redistribution to keep routes short.

• Can’t I just use the redistribute command to set metrics coming in and out of all the IGPs to keep the looping routes out?

Yes, you can.  If you have a small network, that shouldn’t be a problem.  If you have a couple thousand routes, though, I’m sure people have better things to do than manage metrics.

• In what order do you configure the metrics when redistributing into EIGRP?

Bandwidth, delay, reliability, load, and MTU

• What’s weird about an extended ACL when using them with route filtering?

When matching routes, an extended ACL will use the ACL’s source field as the network of the route and the destination field as the subnet mask.  For example, access-list 101 permit ip host 172.16.0.0 host 255.255.255.0 matches 172.16.0.0/24.

• What can’t route-maps do other clean the dishes?

They’re used in many, many places on a Cisco router.  I imagine there’s a macro somewhere that will clean the dishes, though.

What Command Was That

What command…

• …shows the metric of the route you just redistributed into EIGRP?

show ip eigrp topology

• …shows the metric of the route you just redistributed into OSPF?

show ip ospf database external

• …shows the tag of a route?

show ip route

• …shows the admin distances you’ve messed up?

show ip protocols

• …shows the admin distance of a particular route?

show ip route x.x.x.x y.y.y.y

Aaron Conaway

I like to lean my head to the left, hit it with the palm of my right hand, and document what knowledge falls out.

Website - More Posts

Study Questions

• When you redistribute OSPF into EIGRP, what are you really redistributing?

Routes knows via OSPF
Networks of OSPF-enabled interfaces

• What’s the default cost of an EIGRP route redistributed into OSPF?

20

• What’s the default metric of an OSPF route redistributed into EIGRP?

There is none since EIGRP has all those nifty k-values that have to be processed.  Routes actually won’t redistribute without them.

• How do you set the metrics of a route redistributed into EIGRP?

Set the default metric with the default-metric subcommand
Set the metric in the redistribute … metric subcommand
Set the metric with a route-map in the redistribute … route-map subcommand

• If you have a default metric set under EIGRP and a metric set on a redistribution of OSPF, which does the router use?

The router uses the metric for the redistribution.

• What’s special about the metric when redistributing one EIGRP AS into another?

The metric is copied from one AS to the other.

• What is I redistribute one OSPF domain into another?

The same thing happens – the metric is copied from the originating domain.

• What’s the difference in AD between an EIGRP and an external EIGRP route?

EIGRP: 90
External EIGRP: 170  [Didn't I do a blog post about this last month?]

• What’s the difference between an external type 1 and  an external type 2 OSPF route?

External 2 routes, only the external cost is used; no router increments the cost.  For external 1 routes, the external cost is incremented by each route with the internal cost.

• Which of O E1 and O E2 routes is more preferred and why?

E1s are preferred because they’re considered more accurate.  [Didn't I blog on this last month, too?]

• I have redistribute eigrp 1 configured in my OSPF config, but 10.0.0.0/24 isn’t showing up in OSPF.  What gives?

OSPF only redistributes classful routes unless you add the subnets option to the redistribution command.

• What are the options in the redistribute directive when redistributing OSPF into EIGRP?

redistribute ospf process-id [ metric bandwidth delay reliabilityload  mtu ] [ match { internal | nssa-external | external 1 | external 2 } ] [ tag tag-value ] [ route-map route-map ]

• What are the options in the redistribute directive when redistributing EIGRP into OSPF?

redistribute ospf process-id [ metric metric ] [ metric-type metric-type ] [ match { internal |nssa-external | external 1 | external 2 } ] [ tag tag-value ] [ route-map route-map ] [ subnets ]

• What do type-4 LSAs do?

If an external route comes from another area, the ABR uses type-4 LSAs to advertise the cost of the route from the ABR to the ASBR.  Routes use this cost as a tie breaker if the internal cost is the same from two ABRs.

• What type of LSA are used to flood routing advertisements from an external NSSA area into area 0?

The NSSA ASBR uses type-7s to flood into the NSSA, but the ABR to area 0 converts those to type-5s.

What Command Was That

What command…

• …show all the EIGRP routes that originated from other routing protocols?

show ip route eigrp | inc ^D EX

• …shows all the OSPF routes that originated from other routing protocols?

show ip route ospf | incl ^O E[12]

• …show all the type-4 LSAs floating around in an OSPF area?

show ip ospf database asbr-summary

• …show the cost to get from a router to an ASBR?

show ip ospf border-routers

Aaron Conaway

I like to lean my head to the left, hit it with the palm of my right hand, and document what knowledge falls out.

Website - More Posts