flat network to vlan network

[raysm]

can a flatnetwork talk to a vlan based network?

If it is possible let me know how to do it

[Kevin Dorrell]

Yes sure. The flat network is already effectively a VLAN network ... usually on on VLAN 1. Just as you use a router to route between VLANs, you can use a router to route between VLAN 1 and other VLANs.

Kevin Dorrell

Luxembourg

[raysm]

Thanks in this case, my switch ports in the flatnetwork should it be changed to vlan 1?

[Kevin Dorrell]

VLAN 1 is the default. What are they set up to now? They can probably stay where they are, but that is the VLAN you will have to route into your multi-vlan network.

KJD

[raysm]

Hi KJD ,

My situation like this

old network------router----wan

(no vlan specified in ports, also few sgments specified and routed via the router)

new network (L3)

(same segments specified as vlan's)

and now planning to move the router and wan linksto the new network. So built a trunk from old to new network.

Idea is to move the servers in the old network can be moved to new network stage by stage

but the old network server cannot talk to the new

[Kevin Dorrell]

OK, that could be for any number different reasons. All the ports on the old network are in VLAN 1. I have a number of suggestions, but before I go running down the wrong track, could you tell me:

1. Does the new network have a VLAN 1?

2. Is VLAN 1 of the new network on the same IP subnet as the old network?

3. Does the router on the new network have an IP address in VLAN 1?

4. How is the default gateway set in the old server?

5. When you say "the old network server cannot talk to the new", which VLAN are you trying to get to, via which router?

Kevin Dorrell

Luxembourg

[raysm]

Hi Kevin

Thanks again so much to help me

All the ports on the old network are in VLAN 1.

----you mean to say all ports in the old network are in vlan 1 by default. though i dont specify in the ports ..switchport access command

1. Does the new network have a VLAN 1?

no

2. Is VLAN 1 of the new network on the same IP subnet as the old network?

new network i have vlan 10, vlan 20 ..etc

old network one ip segment equal to new network vlan 10

the next segment vlan 20

3. Does the router on the new network have an IP address in VLAN 1?

now vlan 19

4. How is the default gateway set in the old server?

pointing to the router. but this gw will be removed and put in the L3 in new network

5. When you say "the old network server cannot talk to the new", which VLAN are you trying to get to, via which router?

old network (vlan 1) --via trunk new network vlan 10, 20 or 30

[raysm]

Hi kevin

waiting for your answer

and i made a typo error . answer for your q3 is - no vlan 10

[Kevin Dorrell · Accepted solution]

Hello again Danyal,

Sorry for the delay; family takes priority on a Sunday. But I have been thinking about your postings, and I think we have been talking at cross-purposes. I did not understand the full implications of your original question, and the answer I gave may have been misleading.

Your original question was "Can a flatnetwork talk to a vlan based network? My answer should have been "Yes sure, as long as they are not using overlapping IP address space. The flat network is already effectively a VLAN network ... usually on on VLAN 1. Just as you use a router to route between VLANs, you can use a router to route between VLAN 1 and other VLANs.

But that does not help you much, because I realise now that what you are trying to do is to split up an existing flat IP network into a series of subnet VLANs, keeping the same IP address space. Isn't that right?

If you are migrating from one address space to another, it is relatively simple to do what you want to do. Just put the new VLANs on different IP address space to the existing VLAN 1, set an interface for VLAN 1 in your new router, and join the old to the new with a trunk. Then make sure the existing network servers use the new router's VLAN1 interface as a default gateway,or set a static route for the new VLANs from your old router to the VLAN 1 address of the new one.

If you want to re-use the existing address space, then this is much more complicated. Yes you can do it with a temporary network address translation scheme, but that may give you more problems than solutions, and may not be worthwhile for a quick migration. It is very difficult to give a detailed migration plan without knowing exactly what ranges of addresses you are using now, where you want to go to, what timescales you have, what are the availability and downtime constraints, and what addresses you have available as temporary homes during the migration. At the very minimum you are going to have to change the default gateway in all your hosts, because they will be on different VLANs and therefore indifferent IP subnet ranges.

To your current problem, that of the old network not talking to the new, there are two reasons: the new router does not have an IP address in VLAN1, and the existing hosts are not yet using that new address.

Sorry, it's a bit difficult to explain this without knowing the real addressing scheme to focus on.

Kevin Dorrell

Luxembourg

[raysm]

Thanks for the advice and the answer over the weekend. I clearly understand now and below is my situation and this is what I am going to do for the migration.

Current network

flat network with few ip segments routed via router/s running hsrp

(actually this is a critical servers and its a DC, truly not good for a DC design:-))

172.29.50.0/26

172.29.50.64/26

172.29.50.128/26

172.29.50.192/26

We bought new L3 /L2 switches and the new network is built with (three layer design) and core running 6509 hsrp

So idea is to move the above segments to 6509. All above segments to be individual vlan

So as for the above discussion it seems

Migration I planned as below

1. I will have vlan 1 in 6509

2. Configure all the above segments for the same

3. trunk between old network and new network

4. move the wan links ( move the router connection from old switch to 6509

5. so old network should be able to communicate to wan via 6509 and all segments within vlan 1

6. move segment by segment by creating new vlan

example - vlan 2 (172.29.50.64/26) in 6590

remove from vlan 1 int at the same time move all the servers in that segment move to new access switches

This is the plan I have

Thanks again for the time

Danyal

[raju]

Hello Danyal,

From your pstings , what I understood is that your Old Network is not a Flat Network and it's a Routed Network (IP subnets ) & WAN links configured in Layer-3 Routers and you have bought a Layer-3 Switching (6509) recently and you want to move all the Old connections (IP subnets and WAN links ) to 6509 .

If my understanding is correct , you don't need to do point No:3 (Trunk between old Network and Network ) instead you can simply go for IP connectivity .

Regards,

Raju

[raysm]

Hi Raju

yes you are correct but the last point move old connection (ipsubnets and wan links) to 6509 , but in 6509 these segments are to be in vlan's

Anyways I will do some testing

[raju]

Hi !

I understood. The typical Layer-3 interfaces (subnets ) in Old Network will become as Vlans in 6509 . Create a connectivity Vlan between old NW & New NW in same subnet say 10.12.10.1/29 in Old NW and 6509 side for connectivity Vlan ip address will be 10.12.10.2 /29 and create a static Routes on both the sides .

Good luck.

[srihari_par]

hello raysm

i have generally followed the chain on flat network

to vlan, but this point of having a trunk between

old NW and the new NW is not clear to me since i am

a "newbie" to VLAN concepts. could you give me

any urls where more information on VLANs may be

found ?

thanks

srihari