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>1) If proxy arp is enabled on the gigaswitch/fddi, what addresses should be
> assigned to the gigaswitch/fddi ports given that all subnets are on all
> ports? I have read differing opinions from the previous notes. One
..as you mention, this is an unresolved topic of discussion. The
belief is that you are *SUPPOSED* to get proxy ARPs regardless of the
subnet assignments, but I personally don't believe this to actually be
the case in real life.
I haven't actually tested and verified this behaviour, so I have no
proof.
Regardless, ARPs will work - it's just a question of whether or not
the GIGAswitch/FDDI system will be giving you the responses or letting
the end system respond.
The most conservative thing to do is to assign an IP address in
every subnet to all the ports. However, this typically leads to
maxing out the address assignments pretty quickly now that virtual
ports have entered into the equation.
> indicated that you should assign an ip address to the port from the
> subnet to which it connects. I can't do this since I have multiple subnets
> per port. Can a port have multiple address? If it can, should I assign one
Yes.
> address from each subnet. Another opinion is to assign the same ip address
> to all ports. Will this only support ARP serving for the subnet assigned
> to the gigaswitch ports? If the ports were assigned different ip addresses
> all from the same subnet, what would be the effect?
...as I mentioned before, there is some disagreement as to what the
actual behaviour would be.
Assigning different IP addresses from the same subnet would be a
complete waste of time and resources.
>2) If a gigaswitch port has an ip address assigned and a management station
> pings this address, does the port itself respond or does the SCP?
All external communication with the GIGAswitch/FDDI system is with
the SCP.
>3) It doesn't appear that ipswitching can be used in this environment because
> all subnets appear on all ports. Can the gigaswitch provide ipswitching
> by learning all mac addresses for all ip addresses or through another
> mechanism.
...if you haven't done so, you really ought to read the IP switching
paper - there's a pointer in 909.1 "IP switching" has different
implications on the GIGAswitch/FDDI system.
> I've been reading the notes however none of the examples ever uses
>a multihomed environment. Probably with good reason :^)
....I don't think so...
MDL
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Micheal,
We are running gigaswitches with V2.2
>The belief is that you are *SUPPOSED* to get proxy ARPs regardless of
>the subnet assignments, but I personally don't believe this to actually
>be the case in real life.
I agree. The gigaswitches do not appear to proxy arp for hosts outside
of they're subnet assignments. I looked at the arp cache on the
gigaswitches from netview to verify.
> Assigning different IP addresses from the same subnet would be a
> complete waste of time and resources.
This is what I had done when setting up the switch for two reasons.
It wasn't clear how these should be assigned and I need to set something
for arp servering to be enabled. Also I thought I would be able to
determine if an interface was up or down via an snmp management
station. If an interface/bridge port is broken, will the SCP respond
to a ping for the address assigned to the port which has failed?
It would appear that inorder for proxy arp to work in this environment
I will have to set up each port with an address from each subnet.
> ...if you haven't done so, you really ought to read the IP switching
> paper - there's a pointer in 909.1 "IP switching" has different
> implications on the GIGAswitch/FDDI system.
Some bed time reading last night. As with the arp servering I will
need to set up each port with an address from each subnet. Also set up
the decnis(s) to do proxy arp. This will at least eliminate the
current requirement for decnis(s) to act as a one arm routers
effectively doubling the intersubnet traffic on our lan.
Scott
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| > We are running gigaswitches with V2.2
I *strongly* recommend that you upgrade to BL 3.1
> for arp servering to be enabled. Also I thought I would be able to
> determine if an interface was up or down via an snmp management
> station. If an interface/bridge port is broken, will the SCP respond
> to a ping for the address assigned to the port which has failed?
That isn't the way it works. SNMP communication is with the SCP,
and has no bearing on any line card status. You are *not* talking to a
line card, although technically, your communication passes across a
line card to get to the SCP. Note that it doesn't necessarily pass
across the line card to which you have assigned that particular IP
address. You can *not* get any useful information about line card
status from doing pings. You must use the MIB objects for that line
card to get a proper status.
> It would appear that inorder for proxy arp to work in this environment
> I will have to set up each port with an address from each subnet.
This is true in the sense that the GIGAswitch/FDDI system won't
serve all the ARP messages which it could serve. However, this doesn't
mean that ARP won't work, or that the GIGAswitch/FDDI system isn't
serving ARPs.
MDL
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