thank you for your response. I'm still looking it over, but: if I ping -I eth1 10.10.6.254 it works. If I ping -I eth1 10.10.5.254 it does not work. The reverse is true of pinging from eth0. It can ping its default gateway, but cannot ping eth1's default gateway of 10.10.6.254 on the switch.

eth0 - 10.10.5.0/24 def. gateway = 10.10.5.254

eth1 - 10.10.6.0/24 def. gateway = 10.10.6.254

2 default gateways for your box ?? so if you try to reach, say, google, you send it both to eth1 to 10.10.6.254 AND to eth0 to 10.10.5.254 ???

stick with 1 default gateway (that's its purpose: to be the gateway where everything NOT reachable directly via the Ethernet layer is sent to the (SINGLE) default gateway, UNLESS for some specific other LANs you define another special gateway to reach those...

Oh no, I'm sorry, I just defined the def. gateways for those subnets on the switch level.

there is only one default gateway on the box and it is: 10.10.5.254

to debug your setup: imagine you ARE the IP packet: you have a source IP, a destination IP. Now, on the interface you sit on, see what routes will lead to to where (and ensure that machine's setup allows you to, for example on the eth0/eth1 machine, it needs ipforward to go from one interface to the other). And proceed, one hop at a time, toward your goal (AND back to your source : sometimes the destination machine's route/defaultgw are broken and therefore the reply packet is not sent via the right path)

Hi, a chat was suggested by the site so I'm trying it out

hi

read the last versino of my answer, it gives you a way to debug ANY network problem...

If you want me to try, tell me exactly : ALL your local LAN's (10.10.5.0/24, 10.10.6.0/24 : any other?)

and tell me which gateway(s) you have defined to route packets from a LAN to another LAN (ie, yourbox have 2 interfaces, and can be the main gateway between 10.10.5.x/24 and 10.10.6.x/24. Any other? for example : the machine with 10.10.5.254 have how many interfaces? and what is on each interface's sides?)

there are so many ways to setup networks, lans, etc : you could have 2 lans on one side, 4 on the other, and internet in between (and a vpn)... anything is possible. So I really need a detailled view to help further.

right now I assumed you had another (3rd) lan (10.x.y.0/24) because you talk about 'other lans' ...

are you there?

tell me what you see with : cat /proc/sys/net/ipv4/ip_forward

(as you say that on "yourhost" you can NOT ping from one interface to the other??)

are you there?

oh sorry

was talking to my networking ugy

think we might have figured out what's going on, it might be a bug in OEL v6.x because we have machines that run OEL 5.x that don't have this problem

check their routes ^^

and ip_forward on any mchine that ahve several interfaces and that need to act as a gateway for other machines

and recent machines could have ipv6 ... making things more difficult

+ firewalls

ie, many things to check before assuming it's a bug

I'll have to go soon : is your question resolved?

no not yet, but you've been very helpful

thanks for taking the time

i'll let ya go

try my trick (for any ipv4 problems: going from hop to hop, each time ensuring the packet is allowed (route, and ipforward, and internal/external firewall) to go to the next stop, is actually the fastest and "fullest" way to debug any (ipv4) network problems

(also for ipv6, but things change in the way packets travel.. i'm no good on ipv6 yet)

+ checking the way back

(I've seen people going all the way to The Internet, but forgotting to set NAT on the router's outgoing interface ! so the internet next hop received some "10.x.y.z" packet as source, and discarded it pronto

good luck, and i'll reconnect later tonight, to check on that question... If you need further help, please detail the LANs, interfaces, which machines are ip_forwarding, which are routers, what is on each side of machines/routers with several interfaces.

bye