Cisco – Configure Cisco ASA in Transparent mode: Layer2 DMZ w/ Vlan translation

ciscocisco-catalystethernetfirewallvlan

I am in the middle of a project to migrate some existing switched ethernet dot1q trunks behind an ASA firewall… these trunks have five vlans each (numbered 51 – 55). This is a simple drawing of the original layer2 service…

VLAN_Translation_00

One of the requirements is to have an ASA firewall context per Vlan in the original dot1q trunk. This means I wind up using a BVI to bridge the new INSIDE interface to the DMZ interface in each FW context. Due to other constraints, I wind up with a FW config like this (I am summarizing out all the context stuff to simplify the question)…

firewall transparent
!
interface GigabitEthernet0/1.51
 vlan 51
 nameif INSIDE
 security-level 100
 bridge-group 1
!
interface GigabitEthernet0/2.951
 vlan 951
 nameif DMZ
 security-level 50
 bridge-group 1
!
interface BVI1
 ip address 10.10.51.240 255.255.255.0 standby 10.10.51.241
!

Cisco ASAs in transparent mode wind up using two different vlan IDs to connect a single layer2 vlan service. Connect the two vlans through interface BVI1; the bridge-group 1 configuration on each physical interface makes the connection between Vlan51 and Vlan951 in the config above.

Assume ASA:Gi0/2 connects to 4507:Gi1/2… Notice what happens to the DMZ interface… the ASA DMZ Vlan is 951, and this connects via a dot1q trunk to the DMZ switch (the Cat4507). I need to connect D1 to switchport 4507:Gi1/1, but I must deliver the Vlan951-955 services to D1 as dot1q Vlan51-55 on 4507:Gi1/1. In other words, the Vlan BVI wrangling I had to do on the ASA messes up the Vlan numbering in my original service definition.

VLAN_translation_01

Sadly, I cannot easily renumber the Vlans on D1. The perfect solution would be to somehow translate Vlan951 on 4507:Gi1/2 to Vlan51 on 4507:Gi1/1. Cisco has a feature called vlan mapping, but it seems to require QinQ… all my services are simple dot1q… the 4500 vlan mapping docs are not clear about how they handle simple dot1q encapsulation.

I know I can translate the vlans in the 4500 via loopback cable, but this burns two extra ports per Vlan… a total of ten extra ports for all the Vlans in the service (v51 – v55).

Question

Refer to the diagram below.

VLAN_translation_01

How can I translate all Vlans numbered 95x on the 4507:Gi1/2 dot1q trunk to be numbered Vlan5x on 4507:Gi1/1 dot1q? I need to use the fewest number of ports consumed for "translation overhead". Please include configs for all ports that your answer requires.

I am open to vlan mapping, if someone can explain how it would work in this topology…

Equipment

  • 4507R+E, Sup7L-E with IOS XE 3.4.0
  • ASA5555X with 9.0(2)

Best Answer

I don't have SUP7 to test, but it works on SUP6 and SUP32, I would presume SUP7 retains this functionality.

I've tested between JNPR M320 <-> SUP32, and 'vlan mapping JNPR SUP32' works just fine.

There is no need for QinQ, what the QinQ option does is it adds top tag to one particularly tag. So switchport vlan mapping 1042 dot1q-tunnel 42 would map incoming [1042] stack to [42 1042] stack. As opposed to switchport vlan mapping 1042 42 which maps incoming dot1q Vlan [1042] to dot1q Vlan [42].

JNPR M320 config:

{master}[edit interfaces ge-0/1/0 unit 1042]
user@m320# show 
vlan-id 1042;
family inet {
    address 10.42.42.1/24;
}
{master}[edit interfaces ge-0/1/0 unit 1042]
user@m320# run show interfaces ge-0/1/0               
Physical interface: ge-0/1/0, Enabled, Physical link is Up
  Interface index: 135, SNMP ifIndex: 506
  Description: B: SUP32 ge5/1
  Link-level type: Flexible-Ethernet, MTU: 9192, Speed: 1000mbps, BPDU Error: None,
  MAC-REWRITE Error: None, Loopback: Disabled, Source filtering: Disabled, Flow control: Disabled,
  Auto-negotiation: Enabled, Remote fault: Online
  Device flags   : Present Running
  Interface flags: SNMP-Traps Internal: 0x4000
  CoS queues     : 8 supported, 8 maximum usable queues
  Current address: 00:12:1e:d5:90:7f, Hardware address: 00:12:1e:d5:90:7f
  Last flapped   : 2013-02-19 09:14:29 UTC (19w6d 21:12 ago)
  Input rate     : 4560 bps (5 pps)
  Output rate    : 6968 bps (4 pps)
  Active alarms  : None
  Active defects : None
  Interface transmit statistics: Disabled

SUP32 config:

SUP32#show run int giga5/1
Building configuration...

Current configuration : 365 bytes
!
interface GigabitEthernet5/1
 description F: M320 ge-0/1/0
 switchport
 switchport trunk encapsulation dot1q
 switchport mode trunk
 switchport nonegotiate
 switchport vlan mapping enable
 switchport vlan mapping 1042 42
 mtu 9216
 bandwidth 1000000
 speed nonegotiate
 no cdp enable
 spanning-tree portfast edge trunk
 spanning-tree bpdufilter enable
end

SUP32#show ru int vlan42
Building configuration...

Current configuration : 61 bytes
!
interface Vlan42
 ip address 10.42.42.2 255.255.255.0
end

SUP32#sh int GigabitEthernet5/1 vlan mapping  
State: enabled
Original VLAN Translated VLAN
------------- ---------------
  1042           42  

SUP32#sh int vlan42                           
Vlan42 is up, line protocol is up 
  Hardware is EtherSVI, address is 0005.ddee.6000 (bia 0005.ddee.6000)
  Internet address is 10.42.42.2/24
  MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec, 
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive not supported
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input 00:00:09, output 00:01:27, output hang never
  Last clearing of "show interface" counters never
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
  Queueing strategy: fifo
  Output queue: 0/40 (size/max)
  5 minute input rate 0 bits/sec, 0 packets/sec
  5 minute output rate 0 bits/sec, 0 packets/sec
  L2 Switched: ucast: 17 pkt, 1920 bytes - mcast: 0 pkt, 0 bytes
  L3 in Switched: ucast: 0 pkt, 0 bytes - mcast: 0 pkt, 0 bytes mcast
  L3 out Switched: ucast: 0 pkt, 0 bytes mcast: 0 pkt, 0 bytes
     38 packets input, 3432 bytes, 0 no buffer
     Received 21 broadcasts (0 IP multicasts)
     0 runts, 0 giants, 0 throttles 
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     26 packets output, 2420 bytes, 0 underruns
     0 output errors, 0 interface resets
     0 output buffer failures, 0 output buffers swapped out

And 

SUP32#ping 10.42.42.1

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.42.42.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/1 ms
SUP32#sh arp | i 10.42.42.1
Internet  10.42.42.1             12   0012.1ed5.907f  ARPA   Vlan42
SUP32#show mac address-table dynamic address 0012.1ed5.907f
Legend: * - primary entry
        age - seconds since last seen
        n/a - not available

  vlan   mac address     type    learn     age              ports
------+----------------+--------+-----+----------+--------------------------
Active Supervisor:
*  450  0012.1ed5.907f   dynamic  Yes          0   Gi5/1
*   50  0012.1ed5.907f   dynamic  Yes          0   Gi5/1
*   40  0012.1ed5.907f   dynamic  Yes          0   Gi5/1
*   42  0012.1ed5.907f   dynamic  Yes          5   Gi5/1


user@m320# run ping 10.42.42.2 count 2 
PING 10.42.42.2 (10.42.42.2): 56 data bytes
64 bytes from 10.42.42.2: icmp_seq=0 ttl=255 time=0.495 ms
64 bytes from 10.42.42.2: icmp_seq=1 ttl=255 time=0.651 ms

--- 10.42.42.2 ping statistics ---
2 packets transmitted, 2 packets received, 0% packet loss
round-trip min/avg/max/stddev = 0.495/0.573/0.651/0.078 ms

{master}[edit interfaces ge-0/1/0 unit 1042]
user@m320# run show arp no-resolve |match 10.42.42.2 
00:05:dd:ee:60:00 10.42.42.2      ge-0/1/0.1042        none
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