We are upgrading from ASA5505 to ASA5506-X, but unlike the ASA5505, the new firewall ASA5506-X doesn't have switch ports and does not support vlans on physical interfaces. So, I'm creating vlans on its subinterfaces, assigning an IP address to it, but it doesn't communicate with end devices nor using the layer 3 switch to end devices.

Basically, I'm setting the dhcp server directly on the subinterface of asa5506-x, but it doesn't assign an IP address to the computer (when I connect the computer directly to the interface of asa506-x), the same happens using a switch SG500P.

I can work with the routed interface of the asa5506-x (not sub interface), setup the dhcp server, but then I can't create the vlans on it as it's limited and vlan are only supported on the sub-interfaces of this asa5506-x firewall.

Even if we don't care about the dhcp server for a moment, I simply can't login to the ADSM using the IP address of the sub interface, but if an IP address is given to the physical interface, I can login via the ADSM, I can set up the dhcp server but again no vlans on physical interfaces.

Running config of ASA 5506-X (Note: I'm beginner, and there are some commands I know may be wrong as I was testing)

    ASA Version 9.8(1)
hostname ASA5506-X-1038
enable password $sha512$5000$d7ukqoZ+VKJqA80su8CGvg==$vvuGumvyoey96hWjvIBCtg== pbkdf2

interface GigabitEthernet1/1
 nameif outside
 security-level 0
 ip address dhcp setroute
interface GigabitEthernet1/2
 nameif inside
 security-level 100
 ip address
interface GigabitEthernet1/3
 nameif protrans-int
 security-level 100
 ip address
interface GigabitEthernet1/3.3
 vlan 2
 nameif protrans
 security-level 100
 ip address
interface GigabitEthernet1/4
 no nameif
 no security-level
 no ip address
interface GigabitEthernet1/5
 no nameif
 no security-level
 no ip address
interface GigabitEthernet1/6
 no nameif
 no security-level
 no ip address
interface GigabitEthernet1/7
 no nameif
 no security-level
 no ip address
interface GigabitEthernet1/8
 no nameif
 no security-level
 no ip address
interface Management1/1
 no nameif
 no security-level
 ip address
boot system disk0:/asa981-lfbff-k8.SPA
ftp mode passive
same-security-traffic permit inter-interface
same-security-traffic permit intra-interface
object network obj_any
object network obj-protrans
object network 2
object network real-inside
object network mapped-inside
pager lines 24
logging asdm informational
mtu outside 1500
mtu inside 1500
mtu protrans 1500
mtu protrans-int 1500
no failover
no monitor-interface service-module
icmp unreachable rate-limit 1 burst-size 1
asdm image disk0:/asdm-781-150.bin
no asdm history enable
arp timeout 14400
no arp permit-nonconnected
arp rate-limit 16384
object network obj_any
 nat (any,outside) dynamic interface
object network obj-protrans
 nat (protrans,protrans-int) dynamic interface
object network real-inside
 nat (protrans,protrans-int) dynamic interface
timeout xlate 3:00:00
timeout pat-xlate 0:00:30
timeout conn 1:00:00 half-closed 0:10:00 udp 0:02:00 sctp 0:02:00 icmp 0:00:02
timeout sunrpc 0:10:00 h323 0:05:00 h225 1:00:00 mgcp 0:05:00 mgcp-pat 0:05:00
timeout sip 0:30:00 sip_media 0:02:00 sip-invite 0:03:00 sip-disconnect 0:02:00
timeout sip-provisional-media 0:02:00 uauth 0:05:00 absolute
timeout tcp-proxy-reassembly 0:01:00
timeout floating-conn 0:00:00
timeout conn-holddown 0:00:15
timeout igp stale-route 0:01:10
user-identity default-domain LOCAL
aaa authentication login-history
http server enable
http inside
http protrans-int
http protrans
no snmp-server location
no snmp-server contact
service sw-reset-button
crypto ipsec security-association pmtu-aging infinite
crypto ca trustpool policy
telnet timeout 5
no ssh stricthostkeycheck
ssh timeout 5
ssh key-exchange group dh-group1-sha1
console timeout 0

dhcpd auto_config protrans-int
dhcpd address inside
dhcpd enable inside
dhcpd address protrans
dhcpd enable protrans
threat-detection basic-threat
threat-detection statistics access-list
no threat-detection statistics tcp-intercept
dynamic-access-policy-record DfltAccessPolicy
class-map inspection_default
 match default-inspection-traffic
policy-map type inspect dns preset_dns_map
  message-length maximum client auto
  message-length maximum 512
  no tcp-inspection
policy-map global_policy
 class inspection_default
  inspect dns preset_dns_map
  inspect ftp
  inspect h323 h225
  inspect h323 ras
  inspect rsh
  inspect rtsp
  inspect esmtp
  inspect sqlnet
  inspect skinny
  inspect sunrpc
  inspect xdmcp
  inspect sip
  inspect netbios
  inspect tftp
  inspect ip-options
service-policy global_policy global
prompt hostname context
no call-home reporting anonymous

Kindly help. Thanks!

  • You need to include your configuration, otherwise we can only guess and speculate, which is off-topic here.
    – Ron Maupin
    Commented Aug 23, 2017 at 18:10
  • @RonMaupin, I have included the configuration. Thanks!
    – Anonymous
    Commented Aug 23, 2017 at 18:14
  • How is the switch configured?
    – hertitu
    Commented Aug 25, 2017 at 22:36
  • 1
    Sounds like a switch issue. Plugging a PC in directly won't work unless you configure the same vlan on the PC. Commented Aug 27, 2017 at 23:25
  • Did any answer help you? if so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could post and accept your own answer.
    – Ron Maupin
    Commented Dec 31, 2020 at 5:20

4 Answers 4


On the Primary interface that the sub interfaces are built under you do not need a IP address. You will build sub-interfaces with IP addresses.

Interface GigabitEthernet1/3
no nameif
no security-level
no ip address
Interface GigabitEthernet1/3.1
Vlan 100
nameif Wired_Network
Security-level 100
Ip address
Interace GigabitEthernet1/3.2
Vlan 200
nameif Wireless_network
security-level 100
ip address

Also please ensure the uplink to the L2 switch is a Trunk port to enable multiple Vlans to egress:

interface GigabitEthernet1/0/49
 description Uplink to ASA 
 switchport mode trunk

Make sure the L2 switch also has the Vlans in the database.

Apologies for the "..." as when typing it is listed as a line break but the format pushes all the content together, hope this helps !

  • thanks for reply. I want to tell you that I have already done this configuration, but still after setting up the dhcp server on the firewall sub interface it doesn't assign ip addresses to the hosts connected to layer 3 switch. ALso, I can't access the ADSM using the host connected to switch, which is connected to ASA-5506-X sub interface. Although ip address, if given to physical interface, works fine, I can access the ADSM and set a DHCP server, but then I can't create vlans on it. These are two tests I want to perform.
    – Anonymous
    Commented Aug 23, 2017 at 23:00
  • I'll add the dhcp part to the answer
    – Fixitrod
    Commented Aug 24, 2017 at 5:05

I believe you can associate the interfaces to a vlan. Command vlan X under each interface. This will tag the traffic. link to vlan guide

For any non-directly connected networks make sure you add routes. Also, make sure you have a default route if one is needed.

These are tagged vlans. Your laptop plugging straight in won't work unless you have a nic that you can assign a vlan to. You need a switch with the vlans tagged to interface the ASA.

Once you get the proper uplink in place your dhcp should work from the ASA. Cisco calls their uplink a trunk. It's an interface that tags the required vlans and expects tags (sometimes one untagged vlan is used on the link).

For anyone that has this issue and the dhcp is on a separate server you'll need a dhcp relay. In a switch we use ip helper. In the ASA it's dhcp relay. Here's an example...

dhcprelay server Outside dhcprelay enable inside dhcprelay setroute inside

Here is the guide to help you with dhcp relay .... click-- dhcp relay guide for ASA


to find the source for you DHCP server you just need to use "show route" on this command you can see how your ASA find this ip address. setroute inside its not necesary and "dhcprelay enable " work on subinterfaces you want to use dhcp!


interface GigabitEthernet1/3 nameif protrans-int security-level 100 ip address

interface GigabitEthernet1/3.3 vlan 2 nameif protrans security-level 100 ip address

As per your configuration . Interface ethernet 1/3

Cannot be assigned with ip address . It should be no ip address

Example below

Asa(config)# interfàce ethernet 1/3 ASA(config)#no ip address ASA(config)# security level 100 ASA(config)# no shutdown `

ASA(config)#interface ethernet 1/3.3 Asa(config)#ip address 192 .168.2.3 ASA(config)# security level 100 ASA(config) no shutdown

Modify configuration as above and try

Configure trunk port in switch allowing all Vlans connecting ASA firewall.

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