Lan Routing

Unanswered Question
Jul 26th, 2009

Asume we are having 25 network configured in VLAN & HSRP is also configured for gateway. And useing 4503 Switch for Routing which is best routing protocol & what should we advertise to through which VLAN interface .......

I have this problem too.
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Giuseppe Larosa Sun, 07/26/2009 - 23:09

Hello Kumar,

you need at least one additional L3 interface SVI or routed interface to advertise the client vlans to the core.

The best choice should be point-to-point L3 links between distribution (c4503) and core.

You can use OSPF or EIGRP that are the current best IGPs for an enterprise environment.

OSPF is a standard and allows for multi-vendor support.

EIGRP is cisco proprietary.

Both are classless carry subnet masks and support VLSM (variable length subnet mask).

Both have good convergence that can be tuned and can use some advancements in IP Fast convergence (with the appropriate IOS images)

Hope to help

Giuseppe

Chetan Kumar Ress Mon, 07/27/2009 - 01:01

Ya that is good ....... But my point of view is If i am having 10 SVI interface for different Network then should i advertise all SVI interface to the core or I can advertise default to core .

Giuseppe Larosa Mon, 07/27/2009 - 01:08

Hello Kumar,

usually specific routes are advertised to core.

Advertising a summary route representing the 10 SVI subnets can be seen as a possible optimization.

unless the internet connection is connected to one of these SVI I think that advertising a default route to core it is not appropriate.

It may be core side that could advertise a default route to distribution

Hope to help

Giuseppe

Chetan Kumar Ress Mon, 07/27/2009 - 01:24

Y thats good option ...... to summary the route, but while advertiseing which SVI inter face should used like

router ospf 1

net 10.1.1.0 0.0.0.255 area 0 (Vlan 10)

net 10.1.2.0 0.0.0.255 area 0 (Vlan 20)

net 10.1.3.0 0.0.0.255 area 0 (Vlan 30)

net 10.1.4.0 0.0.0.255 area 0 (Vlan 40)

net 10.1.5.0 0.0.0.255 area 0 (Vlan 50)

passive interface default

no passive interface vlan 10(Router Vlan)

no passive interface vlan 20(Router Vlan)

exit

Here for redcy router is connected to Both L3 switch in different VLAN (Different Subnet)

And senario is Two router and two L3 switch

connected with redcy ......

And same in other L3 switch ......

Giuseppe Larosa Mon, 07/27/2009 - 01:35

Hello Kumar,

to create summary routes you need a multi area OSPF design:

outer ospf 1

net 10.1.1.0 0.0.0.255 area 1 (Vlan 10)

net 10.1.2.0 0.0.0.255 area 1 (Vlan 20)

net 10.1.3.0 0.0.0.255 area 1 (Vlan 30)

net 10.1.4.0 0.0.0.255 area 1 (Vlan 40)

net 10.1.5.0 0.0.0.255 area 1 (Vlan 50)

! links to core in area 0

net 10.1.64.0 0.0.0.255 area 0

! summary route at area border

area 1 range 10.1.1.0 255.255.248.0

Hope to help

Giuseppe

Chetan Kumar Ress Mon, 07/27/2009 - 02:17

Ya its ok my view is ......

Between Router and switch we are using two different network ,Each router two interface are used to connect with a switch .......& both interface are in different network ......

OK then this summary route advertise will be sended through all SVI interface .......so in router i will get multiple HOP.......for same route.......

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