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Lan routing - 2 subnets using single fast ethernet port

 
 
AlexC
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Posts: n/a
 
      10-16-2003
Hi,

I thinking of doing simple lan routing for 2 subnets, I'm also
thinking
of getting a cisco 1721 as the router, I plan to put the fast ethernet
port on the subnet A, then create a sub-interface on subnet B.


cisco 1721
|
|
|
+---------------------+
| |
| 4 port switch |
| |
+---------------------+
| |
| |
| |
subnet A subnet B ( 20 Nodes)
(about 30 Nodes)


I tested this scenario with a Linux(with only 1 NIC). What i did was
make eth0 IP sits on subnet A, and eth0:0 sits on subnet B, and let
them be the default gateway for respecetive subnet nodes, it works
perfectly.

Now my question is, will this work on the Cisco 1721? (i believe it
should
be, just playing safe )

Also, by using only 1 fast ethernet port, will this create bottleneck
or performance issue?


Thanks
 
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Mike
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      10-16-2003
I don't believe it will. I believe that you need at least a 1751. I
don't think the 172x supports trunking and that's what you need for
router on a stick. I think. It also depends on the switch, can you
configure a port to trunk.

When you bonded two addresses to your single physical NIC you still
only had one collision domain.

If all you want to do is replicate what the Linux box was doing then
you can do it with a 1721. You would just apply a "secondary" ip
address to the ethernet interface.

I think

On 15 Oct 2003 19:09:36 -0700, http://www.velocityreviews.com/forums/(E-Mail Removed) (AlexC) wrote:

>Hi,
>
>I thinking of doing simple lan routing for 2 subnets, I'm also
>thinking
>of getting a cisco 1721 as the router, I plan to put the fast ethernet
>port on the subnet A, then create a sub-interface on subnet B.
>
>
> cisco 1721
> |
> |
> |
>+---------------------+
>| |
>| 4 port switch |
>| |
>+---------------------+
> | |
> | |
> | |
> subnet A subnet B ( 20 Nodes)
>(about 30 Nodes)
>
>
>I tested this scenario with a Linux(with only 1 NIC). What i did was
>make eth0 IP sits on subnet A, and eth0:0 sits on subnet B, and let
>them be the default gateway for respecetive subnet nodes, it works
>perfectly.
>
>Now my question is, will this work on the Cisco 1721? (i believe it
>should
>be, just playing safe )
>
>Also, by using only 1 fast ethernet port, will this create bottleneck
>or performance issue?
>
>
>Thanks


 
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AlexC
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Posts: n/a
 
      10-16-2003
> If all you want to do is replicate what the Linux box was doing then
> you can do it with a 1721. You would just apply a "secondary" ip
> address to the ethernet interface.


does that mean it can be done uing 1721? Would it create a bottleneck
on network throuput?
 
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Barry Margolin
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      10-16-2003
In article <(E-Mail Removed)> ,
AlexC <(E-Mail Removed)> wrote:
>> If all you want to do is replicate what the Linux box was doing then
>> you can do it with a 1721. You would just apply a "secondary" ip
>> address to the ethernet interface.

>
>does that mean it can be done uing 1721? Would it create a bottleneck
>on network throuput?


Configure "ip route-cache same-interface" and there shouldn't be any
performance impact.

--
Barry Margolin, (E-Mail Removed)
Level(3), Woburn, MA
*** DON'T SEND TECHNICAL QUESTIONS DIRECTLY TO ME, post them to newsgroups.
Please DON'T copy followups to me -- I'll assume it wasn't posted to the group.
 
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AlexC
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      10-17-2003
> Configure "ip route-cache same-interface" and there shouldn't be any
> performance impact.


that is something new to me, btw I also spotted another low end model
Cisco 837, which has 4 ethernet ports. Anyone know if these 4 ports
can be configure different IPs on each interface? like

interface Ethernet0
.....
interface Ethernet1
....
interface Ethernet2
....
interface Ethernet3
....


???



Barry Margolin <(E-Mail Removed)> wrote in message news:<Nvyjb.66$(E-Mail Removed)3.com>...
> In article <(E-Mail Removed)> ,
> AlexC <(E-Mail Removed)> wrote:
> >> If all you want to do is replicate what the Linux box was doing then
> >> you can do it with a 1721. You would just apply a "secondary" ip
> >> address to the ethernet interface.

> >
> >does that mean it can be done uing 1721? Would it create a bottleneck
> >on network throuput?

>

 
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Barry Margolin
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Posts: n/a
 
      10-17-2003
In article <(E-Mail Removed)>,
AlexC <(E-Mail Removed)> wrote:
>> Configure "ip route-cache same-interface" and there shouldn't be any
>> performance impact.

>
>that is something new to me, btw I also spotted another low end model
>Cisco 837, which has 4 ethernet ports. Anyone know if these 4 ports
>can be configure different IPs on each interface? like


Of course they can, that's the normal way that routers are used.

--
Barry Margolin, (E-Mail Removed)
Level(3), Woburn, MA
*** DON'T SEND TECHNICAL QUESTIONS DIRECTLY TO ME, post them to newsgroups.
Please DON'T copy followups to me -- I'll assume it wasn't posted to the group.
 
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Matthew Melbourne
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Posts: n/a
 
      10-17-2003
In article <vKTjb.87$(E-Mail Removed)3.com>,
Barry Margolin <(E-Mail Removed)> wrote:
> In article <(E-Mail Removed)>,
> AlexC <(E-Mail Removed)> wrote:
> >> Configure "ip route-cache same-interface" and there shouldn't be any
> >> performance impact.

> >
> >that is something new to me, btw I also spotted another low end model
> >Cisco 837, which has 4 ethernet ports. Anyone know if these 4 ports
> >can be configure different IPs on each interface? like

>
> Of course they can, that's the normal way that routers are used.


On the 837, I believe the four Ethernet ports are four ports of a built-in
10/100 Ethernet switch, therefore only a single L3 interface would be
available in the router's configuration.

Cheers,

Matt

--
Matthew Melbourne
 
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AlexC
Guest
Posts: n/a
 
      10-20-2003
I suddenly realize that the single port solution might not work if
we need to use DHCP to assign IP address to these 2 different networks,
we simple wont be able know which nodes "should" belong to which network
as the DHCP request will all come in via the same internet to the router,
anybody deal with this problem before?


Barry Margolin <(E-Mail Removed)> wrote in message news:<vKTjb.87$(E-Mail Removed)3.com>...
> In article <(E-Mail Removed)>,
> AlexC <(E-Mail Removed)> wrote:
> >> Configure "ip route-cache same-interface" and there shouldn't be any
> >> performance impact.

> >
> >that is something new to me, btw I also spotted another low end model
> >Cisco 837, which has 4 ethernet ports. Anyone know if these 4 ports
> >can be configure different IPs on each interface? like

>
> Of course they can, that's the normal way that routers are used.

 
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Ivan Ostres
Guest
Posts: n/a
 
      10-20-2003
"AlexC" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed) m...
> I suddenly realize that the single port solution might not work if
> we need to use DHCP to assign IP address to these 2 different networks,
> we simple wont be able know which nodes "should" belong to which network
> as the DHCP request will all come in via the same internet to the router,
> anybody deal with this problem before?
>
>


Yes, that is a common problem. Most of the time, people don't really care
which host gets address from which subnet. For hosts that need always the
same address, it's a better solution to set static addresses anyway...

Ivan


 
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Andre Beck
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Posts: n/a
 
      10-23-2003
Matthew Melbourne <(E-Mail Removed)> writes:
>
> On the 837, I believe the four Ethernet ports are four ports of a built-in
> 10/100 Ethernet switch, therefore only a single L3 interface would be
> available in the router's configuration.


On a 836 testing 12.3(3)XM (or something like that), four new interfaces
(FastEthernet1 - 4) appeared all of a sudden. The Ethernet0 remained
as a routed interface. I didn't investigate further whether this was just
done so you can modify individual switchport characteristics, or whether
this would allow to turn them into routed ports. Enabling HSRP on this
boxes e0 broke tunneling badly (Fa1 went down and up again when the HSRP
group switched to this box, and at the same time, all tunnels with a
source address borrowed from e0 just died), so I didn't really feel to
push it any further.

--
The _S_anta _C_laus _O_peration
or "how to turn a complete illusion into a neverending money source"

-> Andre "ABPSoft" Beck +++ ABP-RIPE +++ Dresden, Germany, Spacetime <-
 
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