From: Gregory Gombas (ggombas@gmail.com)
Date: Sun Sep 30 2007 - 12:13:04 ART
This one made me do a double take!
I have a hub and spoke frame relay network with R4 as the hub and R1
and R2 are the spokes. All interfaces have CDP enabled.
There is no direct pvc between R1 and R2, and I do not have any
mappings in the frame-relay map output between them.
Somehow R1 and R2 see each other as CDP neighbors! Is R4 (the hub)
supposed to forward CDP packets between spokes?
I thought the frame-relay split horizon rule prevented control traffic
like this from being sent out the same interface?
Here are the interface configurations, cdp outputs, and show
frame-relay map outputs if you're interested:
Rack1R1#sh run int ser0/0
Building configuration...
Current configuration : 242 bytes
!
interface Serial0/0
ip address 129.1.124.1 255.255.255.0
encapsulation frame-relay
cdp enable
frame-relay map ip 129.1.124.2 104
frame-relay map ip 129.1.124.4 104 broadcast
no frame-relay inverse-arp
frame-relay lmi-type cisco
end
Rack1R1#show cdp nei
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
S - Switch, H - Host, I - IGMP, r - Repeater
Device ID Local Intrfce Holdtme Capability Platform Port ID
Rack1SW1 Fas 0/0 132 S I WS-C3560- Fas 0/1
Rack1R2 Ser 0/0 133 R S I 2620XM Ser 0/0
Rack1R4 Ser 0/0 169 R S I 2611XM Ser 0/0.124
Rack1R1#
Rack1R1#show fram map
Serial0/0 (up): ip 129.1.124.2 dlci 104(0x68,0x1880), static,
CISCO, status defined, active
Serial0/0 (up): ip 129.1.124.4 dlci 104(0x68,0x1880), static,
broadcast,
CISCO, status defined, active
Rack1R1#
Rack1R2#sh run int ser0/0
Building configuration...
Current configuration : 242 bytes
!
interface Serial0/0
ip address 129.1.124.2 255.255.255.0
encapsulation frame-relay
cdp enable
frame-relay map ip 129.1.124.4 204 broadcast
frame-relay map ip 129.1.124.1 204
no frame-relay inverse-arp
frame-relay lmi-type cisco
end
Rack1R2#
Rack1R2#show cdp nei
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
S - Switch, H - Host, I - IGMP, r - Repeater
Device ID Local Intrfce Holdtme Capability Platform Port ID
Rack1SW2 Fas 0/0 167 S I WS-C3560- Fas 0/2
Rack1R1 Ser 0/0 156 R S I 2610XM Ser 0/0
Rack1R4 Ser 0/0 143 R S I 2611XM Ser 0/0.124
Rack1R2#
Rack1R2#show frame map
Serial0/0 (up): ip 129.1.124.4 dlci 204(0xCC,0x30C0), static,
broadcast,
CISCO, status defined, active
Serial0/0 (up): ip 129.1.124.1 dlci 204(0xCC,0x30C0), static,
CISCO, status defined, active
Rack1R2#
Rack1R4#show run int ser0/0.124
Building configuration...
Current configuration : 184 bytes
!
interface Serial0/0.124 multipoint
ip address 129.1.124.4 255.255.255.0
cdp enable
frame-relay map ip 129.1.124.2 402 broadcast
frame-relay map ip 129.1.124.1 401 broadcast
end
Rack1R4#
Rack1R4#show cdp nei
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
S - Switch, H - Host, I - IGMP, r - Repeater
Device ID Local Intrfce Holdtme Capability Platform Port ID
Rack1SW4 Fas 0/1 128 S I WS-C3550- Fas 0/4
Rack1SW2 Fas 0/0 131 S I WS-C3560- Fas 0/4
Rack1R1 Ser 0/0.124 121 R S I 2610XM Ser 0/0
Rack1R2 Ser 0/0.124 133 R S I 2620XM Ser 0/0
Rack1R5 Ser 0/0.54 148 R S I 3640 Ser 0/0.54
Rack1R4#
Rack1R4#
Rack1R4#show frame map
Serial0/0.124 (up): ip 129.1.124.2 dlci 402(0x192,0x6420), static,
broadcast,
CISCO, status defined, active
Serial0/0.124 (up): ip 129.1.124.1 dlci 401(0x191,0x6410), static,
broadcast,
CISCO, status defined, active
Serial0/0.54 (up): point-to-point dlci, dlci 405(0x195,0x6450), broadcast
status defined, active
Rack1R4#
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