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This article will present how to configure GETVPN to push policies allowing sending and receiving Security Group Tag (SGT) inserted into encrypted packets. Example will involve two branches tagging all the traffic with specific SGT tags and applying Zone Based Firewall (ZBF) policies based on received SGT tags.
Cisco recommends that you have knowledge of these topics:
The information in this document is based on these software versions:
R3 - border router in Branch1, GETVPN group member
R4 - border router in Branch2, GETVPN group member
R1,R2 - GETVPN Key servers in Central Site
OSPF running on all routers
ACL pushed from KS forcing encryption for traffic between 10.0.0.0/16 <-> 10.0.0.0/16
R3 router is tagging all traffic sent from Branch1 with SGT tag = 3
R4 router is tagging all traffic sent from Branch2 with SGT tag = 4
R3 is removing SGT tags when sending traffic towards LAN (assumption that R5 is not supporting inline tagging)
R4 is removing SGT tags when sending traffic towards LAN (assumption that R6 is not supporting inline tagging)
R4 is having no firewall (accepting all packets)
R3 is configured with ZBF with the following policies:
- accepting all traffic from LAN towards WAN
- accepting only ICMP tagged with SGT=4 from WAN towards LAN
To send policies allowing for sending and receiving tagged packets "tac cts sgt" command needs to be present:
interface Loopback0
ip address 10.0.1.1 255.255.255.0
!
interface Ethernet0/0
ip address 192.168.0.1 255.255.255.0
crypto ipsec transform-set TS esp-aes esp-sha256-hmac
mode tunnel
!
crypto ipsec profile prof1
set transform-set TS
!
crypto gdoi group group1
identity number 1
server local
rekey authentication mypubkey rsa GETKEY
rekey transport unicast
sa ipsec 1
profile prof1
match address ipv4 GET-IPV4
replay counter window-size 64
tag cts sgt
address ipv4 192.168.0.1
redundancy
local priority 100
peer address ipv4 192.168.0.2
router ospf 1
network 10.0.0.0 0.0.255.255 area 0
network 192.168.0.0 0.0.0.255 area 0
ip access-list extended GET-IPV4
permit icmp 10.0.0.0 0.0.255.255 10.0.0.0 0.0.255.255
Configuration for R2 is very similar.
GETVPN configuration is the same as for scenario without SGT tags. LAN interface has been configured with manual trustsec:
crypto gdoi group group1
identity number 1
server address ipv4 192.168.0.1
server address ipv4 192.168.0.2
!
!
crypto map cmap 10 gdoi
set group group1
interface Ethernet0/0
ip address 192.168.0.3 255.255.255.0
crypto map cmap
!
interface Ethernet0/1
ip address 10.0.3.1 255.255.255.0
cts manual
no propagate sgt
policy static sgt 3 trusted
router ospf 1
network 10.0.0.0 0.0.255.255 area 0
network 192.168.0.0 0.0.0.255 area 0
ZBF configuration on R3:
All packets from LAN will be accepted. From WAN only ICMP packets tagged with SGT=4 will be accepted:
class-map type inspect match-all TAG_4_ICMP
match security-group source tag 4
match protocol icmp
!
policy-map type inspect FROM_LAN
class class-default
pass log
policy-map type inspect FROM_WAN
class type inspect TAG_4_ICMP
pass log
class class-default
drop log
!
zone security lan
zone security wan
zone-pair security WAN-LAN source wan destination lan
service-policy type inspect FROM_WAN
zone-pair security LAN-WAN source lan destination wan
service-policy type inspect FROM_LAN
interface Ethernet0/0
zone-member security wan
!
interface Ethernet0/1
zone-member security lan
R4 in Branch2 configuration is very similar except ZBF which is not configured there.
R5 and R6 simulates local LAN in both branches. Example configuration for R5:
interface Ethernet0/0
ip address 10.0.3.10 255.255.255.0
router ospf 1
network 10.0.0.0 0.0.255.255 area 0
Checking if SGT tagging is supported on group member in Branch1 (R3):
R3#show crypto gdoi feature cts-sgt
Version Feature Supported
1.0.8 Yes
Checking if TEK policies pushed to group member in Branch1 (R3) are using SGT:
R3#show crypto gdoi
GROUP INFORMATION
<...some output ommited for clarity...>
TEK POLICY for the current KS-Policy ACEs Downloaded:
Ethernet0/0:
IPsec SA:
spi: 0xD100D58E(3506492814)
transform: esp-aes esp-sha256-hmac
sa timing:remaining key lifetime (sec): expired
Anti-Replay(Counter Based) : 64
tag method : cts sgt
alg key size: 16 (bytes)
sig key size: 32 (bytes)
encaps: ENCAPS_TUNNEL
IPsec SA:
spi: 0x52B3CA86(1387514502)
transform: esp-aes esp-sha256-hmac
sa timing:remaining key lifetime (sec): (1537)
Anti-Replay(Counter Based) : 64
tag method : cts sgt
alg key size: 16 (bytes)
sig key size: 32 (bytes)
encaps: ENCAPS_TUNNEL
Sending ICMP traffic from R6 to R5:
R6#ping 10.0.3.10 repeat 10
Type escape sequence to abort.
Sending 10, 100-byte ICMP Echos to 10.0.3.10, timeout is 2 seconds:
!!!!!!!!!!
Success rate is 100 percent (10/10), round-trip min/avg/max = 1/1/6 ms
Checking if R3 is attaching SGT tag to encrypted packets:
R3#show crypto ipsec sa detail
interface: Ethernet0/0
Crypto map tag: cmap, local addr 192.168.0.3
protected vrf: (none)
local ident (addr/mask/prot/port): (10.0.0.0/255.255.0.0/1/0)
remote ident (addr/mask/prot/port): (10.0.0.0/255.255.0.0/1/0)
Group: group1
current_peer 0.0.0.0 port 848
PERMIT, flags={}
#pkts encaps: 39, #pkts encrypt: 39, #pkts digest: 39
#pkts decaps: 39, #pkts decrypt: 39, #pkts verify: 39
#pkts compressed: 0, #pkts decompressed: 0
#pkts not compressed: 0, #pkts compr. failed: 0
#pkts not decompressed: 0, #pkts decompress failed: 0
#pkts no sa (send) 0, #pkts invalid sa (rcv) 0
#pkts encaps failed (send) 0, #pkts decaps failed (rcv) 0
#pkts invalid prot (recv) 0, #pkts verify failed: 0
#pkts invalid identity (recv) 0, #pkts invalid len (rcv) 0
#pkts replay rollover (send): 0, #pkts replay rollover (rcv) 0
##pkts replay failed (rcv): 0
#pkts tagged (send): 39, #pkts untagged (rcv): 39
<...some output ommited for clarity...>
Checking dataplane counters for GETVPN on group member in Branch2 (R3):
R3#show crypto gdoi gm dataplane counters
Data-plane statistics for group group1:
#pkts encrypt : 53 #pkts decrypt : 53
#pkts tagged (send) : 53 #pkts untagged (rcv) : 53
#pkts no sa (send) : 0 #pkts invalid sa (rcv) : 0
#pkts encaps fail (send) : 0 #pkts decap fail (rcv) : 0
#pkts invalid prot (rcv) : 0 #pkts verify fail (rcv) : 0
#pkts not tagged (send) : 0 #pkts not untagged (rcv) : 0
#pkts internal err (send): 0 #pkts internal err (rcv) : 0
Depending on the platform more details can be revealed using debugs. For example on R3:
R3#debug cts platform l2-sgt rx
R3#debug cts platform l2-sgt tx
Packets received by R3 from LAN should be SGT tagged:
01:48:08: cts-l2sgt_rx:l2cts-policysgt:[in=Ethernet0/1 src=0100.5e00.0005 dst=aabb.cc00.6800] Policy SGT Assign [pak=F1B00E00:flag=0x1:psgt=3]
Also encrypted packets send via the tunnel will be tagged:
01:49:28: cts_ether_cmd_handle_post_encap_feature:pak[36BF868]:size=106 in=Ethernet0/1 out=Ethernet0/0 enctype=1 encsize=0 sgt_offset=18 [adj]:idb=Ethernet0/0 is_dot1q=0 linktype=7 mac_length=22 SGT=3
R3 will accept only ICMP packets tagged with SGT=4 coming from WAN. When sending ICMP packets from R6 to R5:
R6#ping 10.0.3.10 repeat 11
Type escape sequence to abort.
Sending 1, 100-byte ICMP Echos to 10.0.3.10, timeout is 2 seconds:
!
Success rate is 100 percent (1/1), round-trip min/avg/max = 1/1/6 ms
R3 will receive tagged ESP packet, decrypt it. Then ZBF will accept the traffic:
*Mar 17 12:45:28.039: %FW-6-PASS_PKT: (target:class)-(WAN-LAN:TAG_4_ICMP) Passing icmp pkt 10.0.4.10:0 => 10.0.3.10:0 with ip ident 57
Also policy-map will present the counters with the numbers of packet accepted:
R3#show policy-firewall stats all
Global Stats:
Session creations since subsystem startup or last reset 0
Current session counts (estab/half-open/terminating) [0:0:0]
Maxever session counts (estab/half-open/terminating) [0:0:0]
Last session created never
Last statistic reset never
Last session creation rate 0
Maxever session creation rate 0
Last half-open session total 0
policy exists on zp WAN-LAN
Zone-pair: WAN-LAN
Service-policy inspect : FROM_WAN
Class-map: TAG_4_ICMP (match-all)
Match: security-group source tag 4
Match: protocol icmp
Pass
18 packets, 1440 bytes
Class-map: class-default (match-any)
Match: any
Drop
3 packets, 72 bytes
policy exists on zp LAN-WAN
Zone-pair: LAN-WAN
Service-policy inspect : FROM_LAN
Class-map: class-default (match-any)
Match: any
Pass
18 packets, 1440 bytes
When trying to telnet from R6 to R5 - that will be dropped by R3 because telnet was not allowed:
*Mar 17 12:49:30.475: %FW-6-DROP_PKT: Dropping tcp session 10.0.4.10:37500 10.0.3.10:23 on zone-pair WAN-LAN class class-default due to DROP action found in policy-map with ip ident 36123