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Community Member

turning on EIGRP

i'm hoping that i haven't screwed up but here goes.  i replaced an HP L2 switch with a L3 3650 as a core switch.  when i installed the SW i didn't enable routing in an effort to not disturb too much.  but now i would like to move some routing lines from our router to the new switch to reduce some hops.

So my question/s is: what should i expect my switch to do when i enable EIGRP?

will it stop processing traffic until it learns the new routes?  and if so, how long?

Or will i see anything at all?

i'm attaching a quick layout of my network as a reference.

Gary

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Hall of Fame Super Blue

Re: turning on EIGRP

garyrivers wrote:

i'm hoping that i haven't screwed up but here goes.  i replaced an HP L2 switch with a L3 3650 as a core switch.  when i installed the SW i didn't enable routing in an effort to not disturb too much.  but now i would like to move some routing lines from our router to the new switch to reduce some hops.

So my question/s is: what should i expect my switch to do when i enable EIGRP?

will it stop processing traffic until it learns the new routes?  and if so, how long?

Or will i see anything at all?

i'm attaching a quick layout of my network as a reference.

Gary

Gary

Can't read visio's so could you repost as a.jpg,

However as a general answer it's not so much enabling EIGRP and turning on ip routing as the fact that presumably you need to move the IP addresses from the router interfaces to the new L3 vlan interfaces on your switch that would cause some downtime. If this is what you are proposing then i would definitely do this out of hours with some downtime.

Note like i say i'm assuming the default-gateways for your clients are the relevant interfaces on your router and these will need to be migrated to the L3 switch for inter-vlan routing to happen on the switch. In addition you would also need to configure the connection between the L3 switch and the router.

If i am assuming wrongly then let me know. Probably best to see the diagram.

Jon

Silver

Re: turning on EIGRP

A png for Jon.



Hall of Fame Super Blue

Re: turning on EIGRP

Christopher

Thanks for that, although i was wondering why you didn't answer the question as well

Jon

Hall of Fame Super Blue

Re: turning on EIGRP

Gary

Thanks to Chris i can now see the diagram.

It's not clear exactly what you want to move onto the 3560 switch, could you clarify ?

Also, the L3 switches in the diagram, are they running EIGRP and if so are they peering with the router ?

Jon

Community Member

Re: turning on EIGRP

1. Well. My thoughts are to move some of the routing FROM the 47.254 RTR to core SW. As an example, during traceroutes we see traffic going from SW15 to SW12 is going from SW15 up to the RTR and back down to SW12.  What I would like is to reduce some hops by having the traffic hit the core SW and then go on to SW12.

2. Well, I’m kinda embarrassed to say that I checked my SW configs and found RIP running on one and EIGRP running on another one.

So think I’ll need to fix that first.  Maybe not.  What are your thoughts, can I leave RIP alone?

2A.  I'm not sure.  what is that CMD to find out?

Thanks

Hall of Fame Super Blue

Re: turning on EIGRP

garyrivers wrote:

1. Well. My thoughts are to move some of the routing FROM the 47.254 RTR to core SW. As an example, during traceroutes we see traffic going from SW15 to SW12 is going from SW15 up to the RTR and back down to SW12.  What I would like is to reduce some hops by having the traffic hit the core SW and then go on to SW12.

2. Well, I’m kinda embarrassed to say that I checked my SW configs and found RIP running on one and EIGRP running on another one.

So think I’ll need to fix that first.  Maybe not.  What are your thoughts, can I leave RIP alone?

2A.  I'm not sure.  what is that CMD to find out?

Thanks

Gary

So the L3 vlan interfaces are not on the core switch, they are on the L3 switches sw12 and sw15 ?

When you say in the diagram "All devices have 47.254 as default-gateway" do you mean end devices like PCs. That is what is confusing me. Because if sw12 and sw15 are L3 i would have though they would be doing the inter-vlan routing.

We need to understand this before making any changes or you could lose network connectivity.

As for RIP which device is it running on ? RIP should generally be avoided however there are a couple of reasons you might want to run it -

1) if end devices need to receive RIP routes - but note this is not usually a very good idea

2) more likely if you only IP Base on your L3 switches they cannot run full EIGRP only static routes/RIP/EIGRP stub.

So we need to know -

1) where inter-vlan routing is done

2) what feature set you have on all your L3 switches ?

Jon

Community Member

Re: turning on EIGRP

Sorry it took so long to get back:

1) if end devices need to receive RIP routes - but note this is not usually a very good idea

2) more likely if you only IP Base on your L3 switches they cannot run full EIGRP only static routes/RIP/EIGRP stub.

So we need to know -

1) where inter-vlan routing is done

vlan routing is done on all 3 switches listed on that diagram. Especially SW12, it is routing 8 vlans.  i've attached a more complete view of my network so you can see what i'm talking about.


2) what feature set you have on all your L3 switches ?

well each one has a different set

SW12 and 15have IP-BASE-mz

SW27 has IP-SERVICES-mz

I'm not sure what SW8 has: flash:c3750-i9-mz.121-19.EA1c/c3750-i9-mz.121-19.EA1c.bin is what i get with a "sh ver".

i have one other question...what if I was to scale back and just enable ip routing on the core SW, SW27 and NOT move any routes over from the RTR?  would the other switches freak out and drop off-line?

Thanks for your help.

Community Member

Re: turning on EIGRP

here's the .png diagram

Community Member

Re: turning on EIGRP

Jon, i forgot to answer your questions at the top of the page.

So the L3 vlan interfaces are not on the core switch, they are on the L3 switches sw12 and sw15 ?

the L3 are config-ed in SW12, 15 & 8

When you say in the diagram "All devices have 47.254 as default-gateway" do you mean end devices like PCs.

correct, PCs, servers, etc.

Hall of Fame Super Blue

Re: turning on EIGRP

garyrivers wrote:

Jon, i forgot to answer your questions at the top of the page.

So the L3 vlan interfaces are not on the core switch, they are on the L3 switches sw12 and sw15 ?

the L3 are config-ed in SW12, 15 & 8

When you say in the diagram "All devices have 47.254 as default-gateway" do you mean end devices like PCs.

correct, PCs, servers, etc.

Gary

This get more confusing by the minute

You say the L3 vlan interfaces are on the L3 switches and then you say PCs/servers etc. have their default-gateway on the router.

Which is it ? or is it a combination of both ?

Jon

Community Member

Re: turning on EIGRP

Jon, first of all let me say i REALLY apolgize for the confusion!  you're going outta your way to assist so let me see if i can get my garbage together here.

You say the L3 vlan interfaces are on the L3 switches and then you say PCs/servers etc. have their default-gateway on the router.

perhaps i'm not following you. L3 vlan interfaces, what do you mean? just so i know what you are referring to and i don't waste your time.

VLAN 1 (house LAN) PCs, etc have .47.254 as their default gateway.  and the other device on the other VLANs have different GWs respective of their VLAN.

is that what you're asking?

Thanks, Gary

Hall of Fame Super Blue

Re: turning on EIGRP

garyrivers wrote:

Jon, first of all let me say i REALLY apolgize for the confusion!  you're going outta your way to assist so let me see if i can get my garbage together here.

You say the L3 vlan interfaces are on the L3 switches and then you say PCs/servers etc. have their default-gateway on the router.

perhaps i'm not following you. L3 vlan interfaces, what do you mean? just so i know what you are referring to and i don't waste your time.

VLAN 1 (house LAN) PCs, etc have .47.254 as their default gateway.  and the other device on the other VLANs have different GWs respective of their VLAN.

is that what you're asking?

Thanks, Gary

Gary

No need to aplogize. I'm just very wary of suggesting changes if i don't fully understand how it is working.

When i say L3 interface i mean on a L3 switch to route between vlans you create L3 vlan interfaces eg -

int vlan 10

ip address 192.168.5.1 255.255.255.0

and then any client in vlan 10 would have an IP address from the 192.168.5.0/24 subnet and it's default-gateway would be 192.168.5.1. So when you say have L3 switches i was asking whether PCs/servers etc. are in vlans that have vlan interfaces on these L3 switches as opposed to being in vlan 1 and having their default-gateway as 47.254 on the router ?

Jon

Community Member

Re: turning on EIGRP

That have vlan interfaces on these L3 switches as opposed to being in vlan 1 and having their default-gateway as 47.254 on the router ?

that answer would  yes, i have devices behind each SW that are VLAN-ed out and their GW are different than the .47.254.

Gary

Hall of Fame Super Blue

Re: turning on EIGRP

garyrivers wrote:

That have vlan interfaces on these L3 switches as opposed to being in vlan 1 and having their default-gateway as 47.254 on the router ?

that answer would  yes, i have devices behind each SW that are VLAN-ed out and their GW are different than the .47.254.

Gary

Gary

Apologies for not getting back sooner.

If all the vlans except vlan 1 are routed off the L3 switches then the easiest thing to do is -

1) move the vlan 1 default-gateway off the router onto the 3560.

2) create a P2P link between the 3560 switch and the router.

3) turn on ip routing and EIGRP on the 3560

This would mean that vlan 1 is routed off the 3560. You would need IP Services on your L3 switch.

However it's not clear whether the existing L3 switches are using EIGRP to peer with the router as there doesn't seem to be a common subnet ??

Before you do anything you need to work out -

1) that the only vlan routing off the router is vlan 1.

2) whether or not your L3 switches have EIGRP neighborships with this router and if so over what subnet ?? "sh ip eigrp neighbor" on the L3 switches and the router should show you what is happening.

Jon

Community Member

Re: turning on EIGRP

Jon,

can we attack this from another route?

Please refer the attached .png file.....

what if i were to start phasing out the RTR by moving the LANs attached to the RTR and the ASA that connects to the RTR?

And my thoughts are to enable routing on the SW27, gradually move the LANS off of the RTR and ASA.  Then in a one-two punch, shutdown the RTR and re-IP the SW to .254 (the default gateway IP).

But i guess the question still remains, what will happen when i enable EIGRP on SW27?

Thoughts?

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