IPCHAINS vs arp (PPTP context)

IPCHAINS vs arp (PPTP context)

Post by Eric Stratt » Thu, 18 Nov 1999 04:00:00



Hi,

    I have a linux firewall masquerade setup with the typical internal
class C subnet of 192.168.x.0, i.e.

192.168.5.x machines-----hub-------|192.168.5.1 (linux box)
x.x.x.x|---internet

What I don't understand is how arp is suppossed to do anything for me.
I have clients connect to PPTP running on the linux box.  This gives
them a local ip of 192.168.5.32 and a p-to-p of 192.168.5.64.
eth0(192.168.5.1) has a default route that will take incoming packets
and forward them to the local LAN machines just fine with no IPCHAINS
rules.
What happens however(using tcpdump), with no IPC rules, is that an
incoming ping comes in over PPTP, goes on to say 192.168.5.2 and then
returns to the linux box and dies, before going back out over the PPTP
link.
If I set up IPC rules to forward to the PPTP adapter, packets pass just
fine, except for broadcast.  I tried setting up manual routes(can I have
multiple x.x.x.0 routes?), specific IPC's for x.x.x.255, and even
manually modifying the ppp0 subnet mask(w/ifconfig), which it insists on
setting to 255.255.255.255 when it comes up.
I don't really need this part to work, and it seems like other people
have gotten the virtual network to work using IP forwarding.  It seems
to me like arp should do some forwarding for me, or something.  I guess
it is suppossed to setup the routes, but I would like to understand
more.  Any good arp resources(tried linuxdoc.org)? and TCP/IP?

Notable Info on my system:

RH6.1 - 2.2.12 kernel
MS VPN clients
PPTP 1.0
PPP 2.3.10
MSCHAP-V2
proxyarp is on
ipforward is on
route table has
192.168.5.0  255.255.255.0 eth0
192.168.5.32 255.255.255.255 ppp0

Thanks,

Eric

 
 
 

1. IPCHAINS vs arp(PPTP context)

Hi,

    I have a linux firewall masquerade setup with the typical internal
class C subnet of 192.168.x.0, i.e.

192.168.5.x machines-----hub-------|192.168.5.1 (linux box)
x.x.x.x|---internet

What I don't understand is how arp is suppossed to do anything for me.
I have clients connect to PPTP running on the linux box.  This gives
them a local ip of 192.168.5.32 and a p-to-p of 192.168.5.64.
eth0(192.168.5.1) has a default route that will take incoming packets
and forward them to the local LAN machines just fine with no IPCHAINS
rules.
What happens however(using tcpdump), with no IPC rules, is that an
incoming ping comes in over PPTP, goes on to say 192.168.5.2 and then
returns to the linux box and dies, before going back out over the PPTP
link.
If I set up IPC rules to forward to the PPTP adapter, packets pass just
fine, except for broadcast.  I tried setting up manual routes(can I have

multiple x.x.x.0 routes?), specific IPC's for x.x.x.255, and even
manually modifying the ppp0 subnet mask(w/ifconfig), which it insists on

setting to 255.255.255.255 when it comes up.
I don't really need this part to work, and it seems like other people
have gotten the virtual network to work using IP forwarding.  It seems
to me like arp should do some forwarding for me, or something.  I guess
it is suppossed to setup the routes, but I would like to understand
more.  Any good arp resources(tried linuxdoc.org)? and TCP/IP?

Notable Info on my system:

RH6.1 - 2.2.12 kernel
MS VPN clients
PPTP 1.0
PPP 2.3.10
MSCHAP-V2
proxyarp is on
ipforward is on
route table has
192.168.5.0  255.255.255.0 eth0
192.168.5.32 255.255.255.255 ppp0

Thanks,

Eric

2. Rebooting HMC and p650

3. IPSec vs. PPTP vs. ?

4. X-window setting?!

5. Linux vs OS2 vs NT vs Win95 vs Multics vs PDP11 vs BSD geeks

6. XFree86 on Compaq Armada 1130?

7. Sunscreen vs. IPchains vs TCPwrappers on Sol9?

8. BIND

9. Ipchains vs Checkpoint vs CyberWall

10. portfw vs. autofw vs. ipchains

11. ipchains & pptp

12. PPTP through IPchains whit masqurade

13. pptp thru ipchains?