"frame-relay fragment" causes link to stop working

[mario_spendier]

Hi people!

I have a strange problem regarding the "frame-relay fragment xyz" command. I have the following configuration:

interface Serial0/0

description R3926704: phy. FrameRelay-Interface (Se0/0)

bandwidth 512

no ip address

max-reserved-bandwidth 95

encapsulation frame-relay IETF

no ip mroute-cache

load-interval 30

no snmp trap link-status

no fair-queue

cdp enable

frame-relay traffic-shaping

frame-relay lmi-type q933a

end

!

interface Serial0/0.1 point-to-point

description YYY: FR-Verbindung zum YY(Se0/0.1)

bandwidth 512

ip address A.A.A.A B.B.B.B

frame-relay class egress_queue_512k

frame-relay interface-dlci 16

end

map-class frame-relay egress_queue_512k

frame-relay cir 486000

frame-relay bc 48600

frame-relay be 0

frame-relay mincir 486000

service-policy output egress_queue

... if i change the map-class to:

map-class frame-relay egress_queue_512k_voice

frame-relay cir 486000

frame-relay bc 4860

frame-relay be 0

frame-relay mincir 486000

service-policy output egress_queue

frame-relay fragment 53

... no traffic goes over the link any more. no telnet no other traffic. the strange thing is, that i can ping the router!??

does anyone know what's the problem here??

thanks for any help!!

Mario

[Brandon Buffin]

Mario,

You need to base the fragment size on the lowest speed link between the 2 routers. If the lowest speed link is 512k, the recommended fragment size is 640 bytes.This is to achieve a 10ms serialization delay. The formula to compute this is Max Delay X Bandwidth. Please see Table 5 in the following link for recommended fragment sizes for 10ms serialization delay for different speed links.

frame-relay fragment command

http://www.cisco.com/en/US/products/sw/iosswrel/ps5187/products_command_reference_chapter09186a008017cf52.html#wp1034268

Hope this helps. If so, please rate the post.

Brandon