Max retransmissions to AP

[Ramprasad2]

HI Team,

i have Cisco 9800 model wlc and ap model 9120axi running version  17.9.3

issue :Max retransmissions to AP 

ap automatic dis join to wlc and automatic join agin

so can we enable in  link latency ? ( if yes what is impact )

can we Adjust MSS size incense ? ( if yes what is impact )

can we Enable Jumbo MTU ? ( if yes what is impact )

[Flavio Miranda]

Hello @Ramprasad2 

 Honest opinion but dont take me wrong, if you dont know the impact dont touch those parameters. I am say that because the impact of those parameters may not be seeing on the device only but on the network as whole. 

MSS and MTU will have effect on how the packet is formed and this will also effect those device that will receive the packet.  Be really careful with MTU and TCP MSS. 

 Link Latency is the least risky among them. What this parameter does is, in case the link between Access Point and the WLC flaps, this parameter will tell the WLC how long it must wait until declare the capwap tunnel  down. If the capwap tunel is stablished over a WAN link, for example, it is a good idea keep it on the maximum value possible. Otherwise, leave it as is. 

[helpdeskggn@konverge.co.in]

Hi @Flavio Miranda 

How to resolve access point automatic join and disjoin the WLC.

when i checked in wlc in join status ( its showing max retransmission to AP )

so any suggestion how to resolve? 

VIP Mentor

[Flavio Miranda]

The problem can be the connectivity between AP and WLC.

 If you ping from wlc to AP, how it looks like? But not normal ping, run the ping for a minutes. Does it drops packets?

[Ramprasad2]

hi @Flavio Miranda 

my production network running 161 ap's and day by day randomly  dis join.

ping is not drop

[Flavio Miranda]

How is your network? It is remote site with wan links? Only central office, both? MPLS? Internet? SDWAN? firewall between AP and WLC?

[Ramprasad2]

@Flavio Miranda 

its manorial design

1 core switch

1.1 wlc connect

1.2 Access switch connect

2 2 access switch connect to AP's

note AP and Access switch and core switch are local put

note AP running in flex connect mode

[Ramprasad2]

hi team,

anyone have  answer ?

[Ramprasad2]

 issue :showing max retransmission to AP

1 core switch

1.1 wlc connect

1.2 Access switch connect

2 2 access switch connect to AP's

note AP and Access switch and core switch are local put

note AP running in flex connect mode

[Ramprasad2]

issue :showing max retransmission to AP

[JPavonM]

This is weird as APs are local to WLC. Check if the L2 topology is stable (STP) and also L3 topology (HSRP).

[Ramprasad2]

@JPavonM 

how to identity L2 topology is stable or not ?

we are not use L3 HSRP

[JPavonM]

Maybe these could be of help for spanning-tree:
https://www.cisco.com/c/en/us/support/docs/lan-switching/spanning-tree-protocol/10556-16.html

What do you use then in your internal topology if not using HSRP, maybe any other FHRP protocol such as VRRP or GLBP? If not, how do you deal with multiple VLANs' SVIs?

[Ramprasad2]

we have used SVI only.

core switch to access switch  L2 etherchannel used with both side activie >

so STP is good and no loops saw any.

so any other ?

[Rich R]

Span the WLC and AP ports and leave a continuous packet capture running on each of the ports.
When you see the AP flap stop both captures and check whether you've had CAPWAP control packet loss (UDP 5246) in either direction.  If so then work out where in the network the drops are happening - congested or erroring interface somewhere maybe.
If not packet drops either end then might be CPU issue on the WLC.  You said 9800 WLC but did not state what model it is - what is the actual WLC model?
"show process cpu platform sorted | incl wncd"
The number of wncd processes depends on the model and the load balancing across them depends on the tagging.
If none of that shows anything useful then open a TAC case with Cisco.