The customer performed a policy change which led to BGP updates being received as malformed packets on the neighbor device with below logs being seen.
%BGP-3-MALFORMED_ATTR: Malformed AS_PATH attribute received from 192.168.1.2
%BGP-4-BAD_UPDATE: Invalid or corrupted update received from neighbor 192.168.1.2, ASN 65001
On customer device, customer made configuration changes on specific routes where they added community value with AS_PREPEND when the neighbour device started reporting malformed BGP update packets on there log messages and routes were not being advertised.
show route advertising-protocol bgp 192.168.1.1 table inet.3 | match 65001
Nov 26 10:13:12
* 10.1.1.1/32 Self 1 [65001] 100 I
* 10.1.1.2/32 Self 1 [65001] 100 I
* 10.1.1.3/32 Self 1 [65001] 100 I
* 10.1.1.4/32 Self 1 [65001] 100 I
From the above output, the AS_PREPEND policy was incorrectly configured by the customer.
Incorrect Configuration :
show policy-options policy-statement AS_PATH_PREPEND
term 10 {
from {
protocol bgp;
prefix-list MY_ROUTES;
}
then {
as-path-prepend "1 65001 100";
accept;
Correct Configuration:
as-path-prepend "65001 65001";
After rectifying the configuration the updates were proper and no further malformed packets were being reported .