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Old 03-05-2010, 08:51 AM   #1
vinaytp
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Registered: Apr 2009
Location: Bengaluru, India
Distribution: RHEL 5.4, 6.0, Ubuntu 10.04
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Routing table


Dear All,

Output of ifconfig is as shown below:

Code:
[vinay@vinay log]$ ifconfig
eth0      Link encap:Ethernet  HWaddr 00:21:86:16:D4:32  
          inet addr:172.17.70.145  Bcast:172.17.70.255  Mask:255.255.255.0
          inet6 addr: fe80::221:86ff:fe16:d432/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:261383 errors:0 dropped:0 overruns:0 frame:0
          TX packets:98351 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:100 
          RX bytes:102189187 (97.4 MiB)  TX bytes:12403896 (11.8 MiB)
          Memory:d0180000-d01a0000 

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:26576 errors:0 dropped:0 overruns:0 frame:0
          TX packets:26576 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:57020168 (54.3 MiB)  TX bytes:57020168 (54.3 MiB)

virbr0    Link encap:Ethernet  HWaddr 00:00:00:00:00:00  
          inet addr:192.168.122.1  Bcast:192.168.122.255  Mask:255.255.255.0
          inet6 addr: fe80::a4dd:ddff:fec0:8f9a/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:61 errors:0 dropped:0 overruns:0 frame:0
          TX packets:54 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:10541 (10.2 KiB)  TX bytes:8507 (8.3 KiB)
My routing table as shown below:

Code:
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
172.17.70.0     0.0.0.0         255.255.255.0   U         0 0          0 eth0
192.168.122.0   0.0.0.0         255.255.255.0   U         0 0          0 virbr0
169.254.0.0     0.0.0.0         255.255.0.0     U         0 0          0 eth0
0.0.0.0         172.17.70.1     0.0.0.0         UG        0 0          0 eth0
The machines which come under 172.17.70.0 address do not require a router/gateway to route the packets.

Also machines that come under 192.168.122.0 are Virtual machines, and they reside in my server. So they too do not need a gateway.

whereas why is gateway not required for the machines that come under 169.254.0.0 newtork ? Also what is the meaning of UG under flags ?

Thanks in advance

Last edited by vinaytp; 03-05-2010 at 08:53 AM.
 
Old 03-05-2010, 08:53 AM   #2
jstephens84
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Registered: Sep 2004
Location: Nashville
Distribution: Manjaro, RHEL, CentOS
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Quote:
Originally Posted by vinaytp View Post
Dear All,

Output of ifconfig is as shown below:

Code:
[vinay@vinay log]$ ifconfig
eth0      Link encap:Ethernet  HWaddr 00:21:86:16:D4:32  
          inet addr:172.17.70.145  Bcast:172.17.70.255  Mask:255.255.255.0
          inet6 addr: fe80::221:86ff:fe16:d432/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:261383 errors:0 dropped:0 overruns:0 frame:0
          TX packets:98351 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:100 
          RX bytes:102189187 (97.4 MiB)  TX bytes:12403896 (11.8 MiB)
          Memory:d0180000-d01a0000 

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:26576 errors:0 dropped:0 overruns:0 frame:0
          TX packets:26576 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:57020168 (54.3 MiB)  TX bytes:57020168 (54.3 MiB)

virbr0    Link encap:Ethernet  HWaddr 00:00:00:00:00:00  
          inet addr:192.168.122.1  Bcast:192.168.122.255  Mask:255.255.255.0
          inet6 addr: fe80::a4dd:ddff:fec0:8f9a/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:61 errors:0 dropped:0 overruns:0 frame:0
          TX packets:54 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:10541 (10.2 KiB)  TX bytes:8507 (8.3 KiB)
My routing table as shown below:

Code:
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
172.17.70.0     0.0.0.0         255.255.255.0   U         0 0          0 eth0
192.168.122.0   0.0.0.0         255.255.255.0   U         0 0          0 virbr0
169.254.0.0     0.0.0.0         255.255.0.0     U         0 0          0 eth0
0.0.0.0         172.17.70.1     0.0.0.0         UG        0 0          0 eth0
The machines which come under 172.17.70.0 address do not require a router/gateway to route the packets.

Also machines that come under 192.168.122.0 are Virtual machines, and they reside in my server. So they too do not need a gateway.

whereas why gateway is not required for the machines that come under 169.254.0.0 newtork ?

Thanks in advance
169.254 is known as apipa. This is basically assigned to network adapters when they either don't have a static IP or can't get a dhcp address.
 
Old 03-05-2010, 09:05 AM   #3
vinaytp
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Registered: Apr 2009
Location: Bengaluru, India
Distribution: RHEL 5.4, 6.0, Ubuntu 10.04
Posts: 704

Original Poster
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Quote:
Originally Posted by jstephens84 View Post
169.254 is known as apipa. This is basically assigned to network adapters when they either don't have a static IP or can't get a dhcp address.
Thank you very much j stephens84.

I can google on APIPA.

What is UG under flags ? what does that mean ?
 
Old 03-05-2010, 11:24 AM   #4
jstephens84
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Registered: Sep 2004
Location: Nashville
Distribution: Manjaro, RHEL, CentOS
Posts: 2,098

Rep: Reputation: 102Reputation: 102
Quote:
Originally Posted by vinaytp View Post
Thank you very much j stephens84.

I can google on APIPA.

What is UG under flags ? what does that mean ?
According to the man pages here is what I found.
Code:
Flags  Possible flags include
              U (route is up)
              H (target is a host)
              G (use gateway)
              R (reinstate route for dynamic routing)
              D (dynamically installed by daemon or redirect)
              M (modified from routing daemon or redirect)
              A (installed by addrconf)
              C (cache entry)
              !  (reject route)
So if I am reading this right it would be saying to use this as a Default gateway and the U is saying the route is up. Also 0.0.0.0 means that all traffic will deafult to this route first unless a static route has been entered.
 
  


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