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

FIB exhausted leads to directed route failure

Publication Date:  2014-05-31 Views:  129 Downloads:  0
Issue Description

The topology is shown as above, S9306 run BGP with up-link router. But S9306-1 cannot ping through S9306-2 when added a new link.
Alarm Information
None
Handling Process
1. Checking interconnected physical link, the status is up
XGigabitEthernet2/0/15 current state : UP
Line protocol current state : UP
Description:connect to Mail9706-2
Switch Port, PVID : 102, TPID : 8100(Hex), The Maximum Frame Length is 9216
IP Sending Frames' Format is PKTFMT_ETHNT_2, Hardware address is ac4e-914d-a4b0
Last physical up time : 2013-10-10 11:00:28
Last physical down time : 2013-10-09 14:15:17
Current system time: 2013-10-10 11:17:54
Port Mode: COMMON FIBER
Speed : 10000, Loopback: NONE
Duplex: FULL, Negotiation: DISABLE
Mdi : NORMAL

2. Checking ARP table, S9306 can learn peer ARP
===============================================
===============display arp===============
===============================================
IP ADDRESS MAC ADDRESS EXPIRE(M) TYPE INTERFACE VPN-INSTANCE
VLAN/CEVLAN
------------------------------------------------------------------------------
211.x.x.226 ac4e-914d-a4bb I - Vlanif100
211. x. x.225 e468-a356-b5d5 20 D-0 XGE2/0/0
100/-
211. x. x.218 ac4e-914d-a4bc I - Vlanif101
211. x. x.217 e468-a356-b5cd 16 D-0 XGE3/0/0
101/-
211. x. x.213 ac4e-914d-a4bd I - Vlanif102
211. x. x.214 ac4e-9148-d8fd 3 D-0 XGE2/0/15
102/-

3. Checking routing tale, there is direct route to peer S9306-2
#
211. x. x.212/30 Direct 0 0 D 211. x. x.213 Vlanif102
211. x. x.213/32 Direct 0 0 D 127.0.0.1 Vlanif102
#

4. Check FIB information using "display fib", there is no FIB entry regarding 211. x. x.212/30. Suspect the route entry too large to load in FIB table. Checking routin-table, 63948 routes in it.
============================================================
===============display ip routing-table===============
============================================================
Route Flags: R - relay, D - download to fib
------------------------------------------------------------------------------
Routing Tables: Public
Destinations : 63672 Routes : 63948

Checking LPU model, it only support 16K FIB entry. The root cause is FIB entry on this LPU exhausted, new added route cannot be loaded in FIB.


5. Aggregate the BGP route within 16K on S9306, the new added route can be loaded in  FIB and the network get through.
Root Cause
Direct connected network barrier is generally caused by the following reasons: 
1 interconnected physical link problem
2. ARP learning problems
3 Direct routing problem
4. FIB table issues
5. Hardware forwarding failures
Suggestions
Trouble shoot directly connected network unreasonable can follow these steps:
Check the physical link -> check the ARP-> check the direct route -> Check FIB table -> hardware forwarding failures

END