IOS uses 4 octet capability

kerstin-534 · ‎09-17-2014

Hi,

have somebody experince with ASA 9.2 or 9.3 BGP implementation. Cannot get it working with BIRD as peer.

Get an malformed AS_PATH

bird> show pro bgp2
name proto table state since info
bgp2 BGP master start 11:26:26 Idle BGP Error: Malformed AS_PATH

protocol bgp bgp2 {
description "ISP";
local as 35000;
neighbor 192.168.0.12 as 15000;
error wait time 9,16;
debug all;
keepalive time 20;
hold time 60;
password "cisco";
export where source=RTS_STATIC;
export where source=RTS_DEVICE;
}

ASA:

router bgp 15000
bgp log-neighbor-changes
address-family ipv4 unicast
neighbor 192.168.0.8 remote-as 35000
neighbor 192.168.0.8 password *****
neighbor 192.168.0.8 version 4
neighbor 192.168.0.8 activate
neighbor 192.168.0.8 filter-list 1 out
redistribute connected route-map isp-out
no auto-summary
no synchronization
exit-address-family

Peering with BIRD works with IOS

Feedback appreciated.

br Fritz

Akash Agrawal · ‎09-18-2014

from RFC 4271

 The AS_PATH attribute is checked for syntactic correctness.  If the
   path is syntactically incorrect, then the Error Subcode MUST be set
   to Malformed AS_PATH.

   If the UPDATE message is received from an external peer, the local
   system MAY check whether the leftmost (with respect to the position
   of octets in the protocol message) AS in the AS_PATH attribute is
   equal to the autonomous system number of the peer that sent the
   message.  If the check determines this is not the case, the Error
   Subcode MUST be set to Malformed AS_PATH.

Please check if you can take wireshark capture or any debug which can tell why as-path is getting corrupted and to what value.

One similar case from google search

http://marc.info/?l=bird-users&m=124515982116091&w=2

Regards,

Akash

kerstin-534 · ‎09-19-2014

IOS uses 4 octet capability in the announcement and 4 octets (AS4) in the Update message.

This works

Internet Protocol Version 4, Src: 192.168.0.50 (192.168.0.50), Dst: 192.168.0.8 (192.168.0.8)
Transmission Control Protocol, Src Port: 33030 (33030), Dst Port: 179 (179), Seq: 3514092093, Ack: 3010016013, Len: 57
Border Gateway Protocol - OPEN Message
Marker: ffffffffffffffffffffffffffffffff
Length: 57
Type: OPEN Message (1)
Version: 4
My AS: 20000
Hold Time: 180
BGP Identifier: 192.168.0.50 (192.168.0.50)
Optional Parameters Length: 28
Optional Parameters
Optional Parameter: Capability
Parameter Type: Capability (2)
Parameter Length: 6
Capability: Multiprotocol extensions capability
Type: Multiprotocol extensions capability (1)
Length: 4
AFI: IPv4 (1)
Reserved: 00
SAFI: Unicast (1)
Optional Parameter: Capability
Parameter Type: Capability (2)
Parameter Length: 2
Capability: Route refresh capability
Type: Route refresh capability (128)
Length: 0
Optional Parameter: Capability
Parameter Type: Capability (2)
Parameter Length: 2
Capability: Route refresh capability
Type: Route refresh capability (2)
Length: 0
Optional Parameter: Capability
Parameter Type: Capability (2)
Parameter Length: 2
Capability: Enhanced route refresh capability
Type: Enhanced route refresh capability (70)
Length: 0
Optional Parameter: Capability
Parameter Type: Capability (2)
Parameter Length: 6
Capability: Support for 4-octet AS number capability
Type: Support for 4-octet AS number capability (65)
Length: 4
AS Number: 20000

Internet Protocol Version 4, Src: 192.168.0.50 (192.168.0.50), Dst: 192.168.0.8 (192.168.0.8)
Transmission Control Protocol, Src Port: 33030 (33030), Dst Port: 179 (179), Seq: 3514092188, Ack: 3010016081, Len: 77
Border Gateway Protocol - UPDATE Message
Marker: ffffffffffffffffffffffffffffffff
Length: 54
Type: UPDATE Message (2)
Withdrawn Routes Length: 0
Total Path Attribute Length: 27
Path attributes
Path Attribut - ORIGIN: INCOMPLETE
Flags: 0x40: Well-known, Transitive, Complete
0... .... = Optional: Well-known
.1.. .... = Transitive: Transitive
..0. .... = Partial: Complete
...0 .... = Length: Regular length
Type Code: ORIGIN (1)
Length: 1
Origin: INCOMPLETE (2)
Path Attribut - AS_PATH: 20000
Flags: 0x40: Well-known, Transitive, Complete
0... .... = Optional: Well-known
.1.. .... = Transitive: Transitive
..0. .... = Partial: Complete
...0 .... = Length: Regular length
Type Code: AS_PATH (2)
Length: 6
AS Path segment: 20000
Segment type: AS_SEQUENCE (2)
Segment length (number of ASN): 1
AS4: 20000
Path Attribut - NEXT_HOP: 192.168.0.50
Flags: 0x40: Well-known, Transitive, Complete
0... .... = Optional: Well-known
.1.. .... = Transitive: Transitive
..0. .... = Partial: Complete
...0 .... = Length: Regular length
Type Code: NEXT_HOP (3)
Length: 4
Next hop: 192.168.0.50 (192.168.0.50)
Path Attribut - MULTI_EXIT_DISC: 0
Flags: 0x80: Optional, Non-transitive, Complete
1... .... = Optional: Optional
.0.. .... = Transitive: Non-transitive
..0. .... = Partial: Complete
...0 .... = Length: Regular length
Type Code: MULTI_EXIT_DISC (4)
Length: 4
Multiple exit discriminator: 0
Network Layer Reachability Information (NLRI)
20.20.0.0/22
NLRI prefix length: 22
NLRI prefix: 20.20.0.0 (20.20.0.0)
Border Gateway Protocol - UPDATE Message
Marker: ffffffffffffffffffffffffffffffff
Length: 23
Type: UPDATE Message (2)
Withdrawn Routes Length: 0
Total Path Attribute Length: 0

kerstin-534 · ‎09-19-2014

ASA anounce 4 Octet capability for AS numbers and 4 byte AS in OPEN message.

ASA uses AS2 attribute in Updates

this works not

Cisco Adaptive Security Appliance Software Version 9.2(2)4

Internet Protocol Version 4, Src: 192.168.0.12 (192.168.0.12), Dst: 192.168.0.8 (192.168.0.8)
Transmission Control Protocol, Src Port: 179 (179), Dst Port: 46026 (46026), Seq: 364474835, Ack: 3117933697, Len: 53
Border Gateway Protocol - OPEN Message
Marker: ffffffffffffffffffffffffffffffff
Length: 53
Type: OPEN Message (1)
Version: 4
My AS: 15000
Hold Time: 180
BGP Identifier: 192.168.2.12 (192.168.2.12)
Optional Parameters Length: 24
Optional Parameters
Optional Parameter: Capability
Parameter Type: Capability (2)
Parameter Length: 6
Capability: Multiprotocol extensions capability
Type: Multiprotocol extensions capability (1)
Length: 4
AFI: IPv4 (1)
Reserved: 00
SAFI: Unicast (1)
Optional Parameter: Capability
Parameter Type: Capability (2)
Parameter Length: 2
Capability: Route refresh capability
Type: Route refresh capability (128)
Length: 0
Optional Parameter: Capability
Parameter Type: Capability (2)
Parameter Length: 2
Capability: Route refresh capability
Type: Route refresh capability (2)
Length: 0
Optional Parameter: Capability
Parameter Type: Capability (2)
Parameter Length: 6
Capability: Support for 4-octet AS number capability
Type: Support for 4-octet AS number capability (65)
Length: 4
AS Number: 15000

Internet Protocol Version 4, Src: 192.168.0.12 (192.168.0.12), Dst: 192.168.0.8 (192.168.0.8)
Transmission Control Protocol, Src Port: 179 (179), Dst Port: 46026 (46026), Seq: 364474926, Ack: 3117933739, Len: 75
Border Gateway Protocol - UPDATE Message
Marker: ffffffffffffffffffffffffffffffff
Length: 52
Type: UPDATE Message (2)
Withdrawn Routes Length: 0
Total Path Attribute Length: 25
Path attributes
Path Attribut - ORIGIN: INCOMPLETE
Flags: 0x40: Well-known, Transitive, Complete
0... .... = Optional: Well-known
.1.. .... = Transitive: Transitive
..0. .... = Partial: Complete
...0 .... = Length: Regular length
Type Code: ORIGIN (1)
Length: 1
Origin: INCOMPLETE (2)
Path Attribut - AS_PATH: 15000
Flags: 0x40: Well-known, Transitive, Complete
0... .... = Optional: Well-known
.1.. .... = Transitive: Transitive
..0. .... = Partial: Complete
...0 .... = Length: Regular length
Type Code: AS_PATH (2)
Length: 4
AS Path segment: 15000
Segment type: AS_SEQUENCE (2)
Segment length (number of ASN): 1
AS2: 15000
Path Attribut - NEXT_HOP: 192.168.0.12
Flags: 0x40: Well-known, Transitive, Complete
0... .... = Optional: Well-known
.1.. .... = Transitive: Transitive
..0. .... = Partial: Complete
...0 .... = Length: Regular length
Type Code: NEXT_HOP (3)
Length: 4
Next hop: 192.168.0.12 (192.168.0.12)
Path Attribut - MULTI_EXIT_DISC: 0
Flags: 0x80: Optional, Non-transitive, Complete
1... .... = Optional: Optional
.0.. .... = Transitive: Non-transitive
..0. .... = Partial: Complete
...0 .... = Length: Regular length
Type Code: MULTI_EXIT_DISC (4)
Length: 4
Multiple exit discriminator: 0
Network Layer Reachability Information (NLRI)
192.168.1.0/24
NLRI prefix length: 24
NLRI prefix: 192.168.1.0 (192.168.1.0)
Border Gateway Protocol - UPDATE Message
Marker: ffffffffffffffffffffffffffffffff
Length: 23
Type: UPDATE Message (2)
Withdrawn Routes Length: 0
Total Path Attribute Length: 0

Cisco ASA BGP with BIRD peering