[SOLVED] CentOS 6.2: Multiple gateways, NIC Problems, Cannot ping all network machines.

K4M5Y5 · 04-15-2012, 10:56 AM

Hello everyone,

I have problem with network, I have tried to solve it, but all solutions didn't help.
I have placed link to PNG which describes network topology it may be useful for better understanding.

http://k4m5y5-h4x0r-1337.net84.net/LQ/topology.png

Problem:
- When two network interfaces are enabled I cannot ping any devices from 172.17.X.*
- When eth2 (WAN) is disabled and eth0 is enabled I'm getting ping from 172.17.X.*

Still I can do ping to router 172.17.100.250 which is connected to eth0 even when both of interfaces are enabled. I'm losing hope to fix the problem.

I need to have access to both of: Internet and Network (left and right side of the attached screen).

Below I have placed some configs from server, if it is not enough please do not hesitate to ask for more.

ifconfig

Code:

eth0      Link encap:Ethernet  HWaddr 00:04:75:B4:55:05  
          inet addr:172.17.100.53  Bcast:172.17.100.255  Mask:255.255.255.0
          inet6 addr: fe80::204:75ff:feb4:5505/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:19540251 errors:0 dropped:0 overruns:0 frame:0
          TX packets:22540837 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:2481040669 (2.3 GiB)  TX bytes:2166254248 (2.0 GiB)
          Interrupt:201 Base address:0xc000 

eth2      Link encap:Ethernet  HWaddr 00:0F:1F:6E:D6:AE  
          inet addr:190.*.*.147  Bcast:190.*.*.151  Mask:255.255.255.248
          inet6 addr: fe80::20f:1fff:fe6e:d6ae/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:3162004 errors:0 dropped:0 overruns:0 frame:0
          TX packets:4273887 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:1025423614 (977.9 MiB)  TX bytes:1026558159 (979.0 MiB)
          Interrupt:217 Memory:fcd00000-fcd10000 

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:52353 errors:0 dropped:0 overruns:0 frame:0
          TX packets:52353 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:14523516 (13.8 MiB)  TX bytes:14523516 (13.8 MiB)

iptables -L

Code:

Chain INPUT (policy ACCEPT)
target     prot opt source               destination         
RH-Firewall-1-INPUT  all  --  anywhere             anywhere            

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination         
RH-Firewall-1-INPUT  all  --  anywhere             anywhere            

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination         

Chain RH-Firewall-1-INPUT (2 references)
target     prot opt source               destination         
ACCEPT     all  --  anywhere             anywhere            
ACCEPT     icmp --  anywhere             anywhere            icmp any 
ACCEPT     esp  --  anywhere             anywhere            
ACCEPT     ah   --  anywhere             anywhere            
ACCEPT     udp  --  anywhere             224.0.0.251         udp dpt:mdns 
ACCEPT     udp  --  anywhere             anywhere            udp dpt:ipp 
ACCEPT     tcp  --  anywhere             anywhere            tcp dpt:ipp 
ACCEPT     all  --  anywhere             anywhere            state RELATED,ESTABLISHED 
ACCEPT     tcp  --  anywhere             anywhere            state NEW tcp dpt:smtp 
ACCEPT     tcp  --  anywhere             anywhere            state NEW tcp dpt:ftp 
ACCEPT     tcp  --  anywhere             anywhere            state NEW tcp dpt:nfs 
ACCEPT     tcp  --  anywhere             anywhere            state NEW tcp dpt:ssh 
ACCEPT     udp  --  anywhere             anywhere            state NEW udp dpt:netbios-ns 
ACCEPT     udp  --  anywhere             anywhere            state NEW udp dpt:netbios-dgm 
ACCEPT     tcp  --  anywhere             anywhere            state NEW tcp dpt:netbios-ssn 
ACCEPT     tcp  --  anywhere             anywhere            state NEW tcp dpt:microsoft-ds 
ACCEPT     tcp  --  anywhere             anywhere            state NEW tcp dpt:telnet 
ACCEPT     tcp  --  anywhere             anywhere            state NEW tcp dpt:http 
ACCEPT     tcp  --  anywhere             anywhere            state NEW tcp dpt:https 
ACCEPT     tcp  --  anywhere             anywhere            state NEW tcp dpt:mysql 
ACCEPT     tcp  --  anywhere             anywhere            state NEW tcp dpt:webcache 
REJECT     all  --  anywhere             anywhere            reject-with icmp-host-prohibited 
ACCEPT     tcp  --  anywhere             anywhere            state NEW tcp dpt:postgres

route -n

Code:

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
190.*.*.144     0.0.0.0         255.255.255.248 U     0      0        0 eth2
172.17.100.0    0.0.0.0         255.255.255.0   U     0      0        0 eth0
169.254.0.0     0.0.0.0         255.255.0.0     U     0      0        0 eth2
0.0.0.0         190.*.*.145     0.0.0.0         UG    0      0        0 eth2

I am waiting for any kind of suggestions...
Best Regards,
Kamil

business_kid · 04-15-2012, 02:40 PM

Can you get in and type
/showing off his tiny bit of cisco knowhow :-)
en
show run
/end his tiny bit of cisco knowhow :-)
and look at the stuff that throws up on the routers. Somethings dropping packets.

baldy3105 · 04-15-2012, 02:47 PM

What does the route table look like when eth2 is down?

K4M5Y5 · 04-16-2012, 08:26 AM

Hello everyone,

Finally I found solution. Guys, You will not believe how simple was that

Client wanted to ping machine which IP address was: 172.17.5.250,
while the router IP is 172.17.100.250 so router assigned net-addresses like:

:: From route -n
NetAddress: 172.17.100.0
NM: 255.255.255.0
GW: 172.17.100.250

When I deleted this position form routing table and added new like this:
NetAddress: 172.17.0.0
NM: 255.255.0.0
GW: 172.17.100.250

Finally it worked fine!
Of course there was need to add ip_forward=1 to sysctl. To make packets going between to GWs.

Thank you for your commitment!

Regards,
Kamil