[c-nsp] A9K-VSM-500

[Aaron Gould]

my personal notes from testing vsm-500 from a few years ago...

*** my testing showed good with pings, BUT TERRIBLE and NON-existent web surfing until changing MTU of vnics from 1514 to 9216

interface TenGigE0/3/1/0
 description vsm
 mtu 9216
!
interface TenGigE0/3/1/1
 description vsm
 mtu 9216
!
interface TenGigE0/3/1/2
 description vsm
 mtu 9216
!
interface TenGigE0/3/1/3
 description vsm
 mtu 9216
!
interface TenGigE0/3/1/4
 description vsm
 mtu 9216
!
interface TenGigE0/3/1/5
 description vsm
 mtu 9216
!
interface TenGigE0/3/1/6
 description vsm
 mtu 9216
!
interface TenGigE0/3/1/7
 description vsm
 mtu 9216
!
interface TenGigE0/3/1/8
 description vsm
 mtu 9216
!
interface TenGigE0/3/1/9
 description vsm
 mtu 9216
!
interface TenGigE0/3/1/10
 description vsm
 mtu 9216
!
interface TenGigE0/3/1/11
 description vsm
 mtu 9216

----------------------------------------------------------------------------------------------

also i have a document but i can't find it online anywhere... it's titled "ASR9K CGv6 on VSM troubleshooting guide"

there is a section subtitled..."3. VSM packet flow troubleshooting"

NOTE 1 : Be aware about CSCuo63064 which explain the packet drops for packet which supposed to be  fragmented on VSM

Symptom: Packets requiring fragmentation are silently dropped with DROP_FRM_FRM_ERR_XAUI9 error count 

Conditions: Observed with NAT44 on VSM with packet sizes above 1514 bytes.

Workaround: Increase the interface MTU on the VSM physical interfaces to match the ingress interface 

More Info: For better NAT44 performance, Cisco recommends keeping the default physical interface MTU 

This one is targetted to be fixed in 5.2.2 XR release

NOTE 2: Be aware about default MTU for ServiceApp interfaces

in 5.1.3 and 5.2.0: MTU is 1514 (not configurable) in 5.2.2: ServiceApp interface will be set by default to Jumbo frame size (not configurable)

CSCuo63064

https://bst.cloudapps.cisco.com/bugsearch/bug/CSCuo63064 

-Aaron