No relevant resource is found in the selected language.

This site uses cookies. By continuing to browse the site you are agreeing to our use of cookies. Read our privacy policy>

Reminder

To have a better experience, please upgrade your IE browser.

upgrade

Problem about Static Routes on the NE80E

Publication Date:  2012-07-27 Views:  73 Downloads:  0
Issue Description
Three uplinks are configured on NE80E-2 and load sharing is implemented among these three static routes.
ip route-static destination IP 255.255.255.255 1.1.1.1
ip route-static destination IP 255.255.255.255 x.x.x.x
ip route-static destination IP 255.255.255.255 y.y.y.y
On NE80E-2, 10G POS port 8/0/0 that connects to another NE80E at 1.1.1.1 is Down.
[NE80E]dis int p8/0/0
Pos8/0/0 current state : DOWN
Line protocol current state : DOWN
, The Maximum Transmit Unit is 4470 bytes, Hold timer is 10(sec)
Internet Address is 1.1.1.1/30
The static route configured by the command ip route-static destination IP 255.255.255.255 1.1.1.1 does not fail. Instead, a static route to NULL0 is generated. In this way, one third of uplink traffic is lost.
[SY-IDC-R2-Pos8/0/0]dis ip rout destination IP
Route Flags: R - relay, D - download to fib
------------------------------------------------------------------------------
Routing Table : Public
Summary Count : 3
Destination/Mask Proto Pre Cost Flags NextHop Interface
Destination IP/32 Static 60 0 RD 1.1.1.1 NULL0
Static 60 0 RD x.x.x. x Pos10/0/0
Static 60 0 RD y.y.y.y Pos12/0/0

After the static route configured by the command ip route-static destination IP 255.255.255.255 1.1.1.1 is manually deleted, the services recover.
[SY-IDC-R2]un ip route-static ip route-static destination IP 255.255.255.255 1.1.1.1
[SY-IDC-R2]dis ip rout destination IP
Route Flags: R - relay, D - download to fib
------------------------------------------------------------------------------
Routing Table : Public
Summary Count : 2
Destination/Mask Proto Pre Cost Flags NextHop Interface
Destination IP/32 Static 60 0 RD x.x.x.x Pos10/0/0
Static 60 0 RD y.y.y.y Pos12/0/0 


 
Alarm Information
Null 
Handling Process

Change ip route-static destination IP 255.255.255.255 1.1.1.1 to ip route-static destination IP 255.255.255.255 Pos 8/0/0 1.1.1.1 and no iteration to the next hop is performed. Thus, the problem can be avoided. 

Root Cause
The analysis based on the available information shows that this problem should have been caused by incorrect route iteration after POS 8/0/0 is Down.
A static route is configured by the ip route-static 202.107.109.220 255.255.255.255 61.189.7.241 command. Since no outbound interface is specified, this static route is not a valid route and a reachable outbound interface needs to be found according to the next hop address 61.189.7.241.
This process is called iteration.
When POS 8/0/0 is Up, there is a direct route from POS 8/0/0 on SY-IDC-R2 to the host at 61.189.7.241 (subnet mask 255.255.255.255). Therefore, the route to 202.107.109.220 can be correctly recurred to POS 8/0/0 and forwarding is normal.
When POS 8/0/0 is Down, the direct route to 61.189.7.241 is deleted. If there is no active route to 61.189.7.241, the original static routes are unable to perform a secondary iteration and become invalid routes. In this case, no traffic is lost.
At this time, however, there is a route to 61.189.7.241 (a static route with the mask less than 32 bits) and the outbound interface is NULL0. As a result, the original static routes rely on this route again to iterate an incorrect outbound interface NULL0, resulting in traffic loss on the link to 61.189.7.241.
A static route is exactly matched, and therefore, re-iteration succeeds and traffic is all recurred to NULL0.
ip route-static 61.189.0.0 255.255.248.0 NULL0 preference 255 
Suggestions
Null 

END