Re: Class C subnetting with PM2e & Ascend P25

John G. Thompson (jgt10@livingston.com)
Wed, 27 Nov 1996 17:29:07 -0800 (PST)

On Wed, 27 Nov 1996, Mick Maldonado wrote:
>
> We are trying subnet a class C with a 27 bit netmask (.224) on a
> Livingston PM2e to provide 8 subnets of 30 hosts per subnet, so that
> our sys admin can dial in via an Ascend Pipeline 25 on an ISDN port and
> have his own 30 host subnet. We have also assigned addresses for 20 or so
> dial-in users in an other subnet. The PM2e is configured by adding
> a netmask to the class C in question (one address of which is on ether0)
> and adding a static route to the Pipeline's Ethernet interface, an address
> on his private subnet:
>
> add netmask 199.199.99.0 255.255.255.224 ;our class C
> add route 199.199.99.96 (his subnet) 199.199.99.97 (his WAN port on the
> P25)
>
> The Pipeline has a LAN port address as well as a WAN (serial) port
> address-- should the gateway for his subnet be the LAN or serial port?

The P25 gateway should be the WAN port or the IP address on the other end.

The LAN network should use the LAN IP address of the P25 for the gateway
address.

> The ISDN link works fine, and telneting into the PM2e, he can ping the
> LAN port on the P25, but when he pings the serial port on the P25, he can
> see packets
> arriving and transmitting but the PM2e never registers the echo packet and
> thinks it's unreachable.

'He' sees packets arriving and leaving where? The P25? Is there a trace
facility on the P25 to report packets?

On the PM is there a icmp packet trace filter running? If a host on the
thernet of the PM tries to ping the WAN of the P25 what does the PM see?

If the P25 tries to ping the PM WAN interface IP what does the PM see?
If the P25 tries to ping the PM ethernet address (if it is different from
the WAN address) what does the PM see?

If a host on the P25 LAN pings the PM's WAN and ethernet address what
does the PM see? If that host pings a host on the PM's LAN what does the
PM see?

To create and use the icmp filter on the PM.

Command> add filter p
Command> set fil p 1 permit icmp
Command> set console
Command> pt p

To end the packet filtering

Command> pt

> Do we need to be dealing with two separate class C's-- one subnetted for
> the assignment pools and one for the segment on ether0?

No. You do need separate 'networks', be they class Cs or subnets.

> Our
> default gateway is an address on the class C in question which is also a
> secondary address on a Cisco 2503 ethernet port which routes to our ISP
> and our other class C networks (secondaries on the same Cisco ethernet
> interface).When we apply the netmask to the class C, packets get lost for other
> dial-up hosts on the PM2e and all heck breaks loose.

Secondary enternet addressing...very nasty stuff when it goes wrong.
Stick to one ethernet network on a physical segement.

Wife just called..gotta go...sory.

JGT

--
John G. Thompson       Livingston Enterprises Inc.    Phone: (800) 458-9966
JOAT(MON)              4464 Willow Road                 Fax: (510) 426-8951
support@livingston.com Pleasanton, CA 94588      http://www.livingston.com