Issue with ethernet interface

Thread Tools Search this Thread
Operating Systems Linux Issue with ethernet interface
# 15  
Old 02-20-2014
hi rbatte1,
once again thank you for your support.
what I do not understand in fact, it is the fact that I need to add a gateway for the network As eth2 (, is in the network and the other equipment (, is also in the same network, then what is the reason to add a gateway between them to communicate? I'm sorry but I still do not understand why the gateway is necessary in this case. if you can provide me more clarifications, it will help me a lot.
please find below ifcfg for eth0 and eth2:
cat /etc/sysconfig/network-scripts/ifcfg-eth0
# Broadcom Corporation NetXtreme II BCM5709 Gigabit Ethernet

[root@sigsrv01 ~]# cat /etc/sysconfig/network-scripts/ifcfg-eth2
# Broadcom Corporation NetXtreme II BCM5709 Gigabit Ethernet
[root@sigsrv01 ~]#

I notify that there is a gateway in the network to permit my server to comunicate with the other network differents of the network and network

# 16  
Old 02-20-2014
Because as I already told you each interface unless they are on same network need their default getaway…
If its too difficult for you to understand, then do this: Give the correct GW to your Eth2 and remove the GW from Eth0, now you tell us what is working
What do you conclude?
# 17  
Old 02-20-2014
We have a terminology problem here. There must be (in general) one gateway per interface. However, there should only be a single default gateway. If there is only one interface and therefore only one gateway it will be the default gateway. If you have several interfaces with several gateways, you must anoint one as the default gateway by putting it in /etc/sysconfig/network. Meanwhile every interface must have its own gateway defined in the interface script.

cerco, suppose that you got your system to work with a single gateway. And assume that from some distant IP address I ping your box on the IP address on eth2. How do you respond? You can't send a packet out eth2, it doesn't know how to reach me (no gateway). Do you send the packet out eth0 to the only gateway you know? What to use for the source IP address? Do I ping one IP address and get and response from a different IP?

I have some more time after all... my meeting just got canceled Smilie

So if you try to reach some distant IP address, with your setup, the default gateway will tell you which interface to use. But if you have decided to use the second interface, you need some gateway for it. If there are just a few hosts that you talk to on the second interface and they are all on the same subnet as your interface you should be ok with no gateway. But that does not seem like what you have.

If the system is using dynamic routing which means that gated is running you can dynamically switch default gateways. This allows the router (which is what your system would be at this point) to adapt to network outages and exploit redunant routes.

Last edited by Perderabo; 02-20-2014 at 06:21 PM..
# 18  
Old 02-21-2014
ok i'll be very simple. my situation is exactly like this:
I have 3 hosts with below configs:
Host A:
eth0: gw
eth2: no gateway

Host B:
eth0: gw
eth2: no gateway

Host C :
eth0: no gateway

the interfaces eth2 (host A), eth2 (host B) and eth0 (host C), are connected on the same switch (network

B is communicating with C without problem (pings are working fine), but it's impossible for A to communicate with C (pings are not working), and with B.

so my problem is, how to do so that A be able to ping B and C.
do you think that in this case it's necessary to configure a gateway from A to permit him to ping B and C? if yes, what IP must I configure for this gateway, as the 3 interfaces (A-eth2, B-eth2 and C-eth0), are already on the same network

hope my explanations are clearer this time, so that you can help me easly.
# 19  
Old 02-21-2014
Based on what you just posted, those adresses should be able to communicate with each other without using a gateway. If they aren't it must be either the routing tables or the configuration of the switch. Are the ports all on the same vlan? Try switching the cables between hosta and hostb.

Are you pinging IP addreses rather than hostnames? Try traceroute to be sure the working system is working the way you think it is.
# 20  
Old 02-21-2014
all ports on the switch are in the same vlan and these ports are working fine. when I try to deconnect hostA from switch and replace it by hostB on the same port, hostB can communicate with hostC (pings are working fine). so i think that the issue come from hostA network config.
I'm pinging IP address and not hostnames

below is the traceroute from A to C:
[root@sigsrv01 ~]# traceroute
traceroute to (, 30 hops max, 40 byte packets
 1  sigsrv01 (  3002.150 ms !H  3002.143 ms !H  3002.133 ms !H
[root@sigsrv01 ~]#

# 21  
Old 02-21-2014
Well, that traceroute helpfully tells us that A cannot talk to C.

A traceroute from B to C might shed some light on how B reaches C.

And a "netstat -rrv" from all 3 hosts would show us the routing tables.

Another idea is a bad network card. Is the link light lit?
Login or Register to Ask a Question

Previous Thread | Next Thread

10 More Discussions You Might Find Interesting

1. UNIX for Advanced & Expert Users

C program to detect duplicate ip address if any after assigning ip address to ethernet interface

Hi , Could someone let me know how to detect duplicate ip address after assigning ip address to ethernet interface using c program (3 Replies)
Discussion started by: Gopi Krishna P
3 Replies

2. IP Networking

Channel bonding Issue - Bond0 interface not getting up in on RHEL6

Hello, I am trying to set up Channel Bonding on a RHEL6 Virtual Box VM. I have 2 ethernet cards on the machine which are set up in Internal Network mode. I followed all the steps exactly as mentioned in the RHEL6 deployment Guide, but for some reason i think results are not correct. Here are my... (13 Replies)
Discussion started by: Rohit Bhanot
13 Replies

3. AIX

interface collisions on ethernet nic

Hi, is there any method to check the interface collisions on ethernet NIC in AIX. I know that in Solaris it's netstat -i but I've written that in AIX it doesn't show this. Thanks&regards, p (1 Reply)
Discussion started by: pitmod
1 Replies

4. IP Networking

Need a bridge from an ethernet interface to a serial interface

This is my situation DOS pc serial cable (sl0) Linux Pc eth1 <--------------------> <------------> (router) I connected the linux pc and the dos pc with a SLIP (serial line internet protocol), so they can communicate in the sl0 interface. ... (3 Replies)
Discussion started by: mghis
3 Replies

5. Solaris

Sun Solaris ethernet interface

Hi, During the installation of solaris suppose I am configuring one ethernet interface that is primary but on my server there are 4 ethernet interfaces,because all other interface not configured, what is way to find out how many ethernet interfaces are there on Server, (6 Replies)
Discussion started by: manoj.solaris
6 Replies

6. Solaris

Network interface issue

Hi All, I want to configure network into my system. i tried following in to configure the interface to find the name of interface #prtdiag |grep net i got following 0 PCI-1 33 1 network-SUNW, hme then i tried following #prtconf -v |grep net network, instance #0 (6 Replies)
Discussion started by: kumarmani
6 Replies

7. Solaris

Ethernet card drivers issue...

I need to install ethernet card drivers on intel machine. How can i know which Ethernet card interface (sfe,rh,rtls...) is it? How can i know the speed of that card? How can i know network traffic ? If network traffic is more with that interface what should i do? Thanks in advance (2 Replies)
Discussion started by: younus_syed
2 Replies

8. Solaris

Network Interface Issue

Hi all, Here im facing problem with NIC Interface with my X86 Version of Solaris Express, even after loading module for that Interface. So please check this below mentioned log for your use and get back to me ASAP. - - - -- --... (0 Replies)
Discussion started by: baraghun
0 Replies

9. SCO

Issue with a ethernet card

Installed a replacement 3com pci card on an ibm PC 300 GL, running OpenServer 6.0 , brought up system, and recieved this message: Fsstat:/dev/boot mounted Mounted /stand filesystem System auditing is not enabled. Dlpid:Unable to open network adapter driver (/dev/mdi/r8e0) Dlpid:No such... (0 Replies)
Discussion started by: tazmss1
0 Replies

10. Programming

determine if a ethernet interface is up

Howto check if a ethernet interface is up? It's impossible to determine via the ipaddress i have learned, or? Can someone please give me a hint on howto do? Environment == Linux x86 GNU GCC. :D regards Esaia (2 Replies)
Discussion started by: Esaia
2 Replies
Login or Register to Ask a Question