ZBFP and self zone policy.
Let’s continue our tests with the ZBPF. Now I’m going to implement L3 firewall (no transparent) and block EIGRP and OSPF packets sent and received on the outside interface (gig0/0).
OUTSIDE L3 firewall INSIDE
[10.0.0.1] [10.0.0.3]
/----\ /----\ /----\
R1 |------| R2 |-------| R3 |
\----/ / \----/ \ \----/
gig0/0 gig0/1
<-X->| <-->
eigrp, ospf
R1:
!
interface GigabitEthernet0/0
ip address 10.0.0.1 255.255.255.0
!
!
router eigrp 1
network 0.0.0.0
!
router ospf 1
log-adjacency-changes
network 0.0.0.0 255.255.255.255 area 0
!
R2:
interface GigabitEthernet0/0
ip address 10.0.0.2 255.255.255.0
!
interface GigabitEthernet0/1
ip address 20.0.0.2 255.255.255.
!
router eigrp 1
network 0.0.0.0
!
router ospf 1
log-adjacency-changes
network 0.0.0.0 255.255.255.255 area 0
!
R3:
!
interface FastEthernet0/0
ip address 20.0.0.3 255.255.255.0
!
!
router eigrp 1
network 0.0.0.0
!
router ospf 1
log-adjacency-changes
network 0.0.0.0 255.255.255.255 area 0
!
Let’s try if each router sees his neighbors:
r1#sh ip eigrp neighbors
EIGRP-IPv4 Neighbors for AS(1)
H Address Interface Hold Uptime SRTT RTO Q Seq
(sec) (ms) Cnt Num
0 10.0.0.2 Gi0/0 14 00:03:38 1 200 0 16
r1#sh ip ospf neighbor
Neighbor ID Pri State Dead Time Address Interface
20.0.0.2 1 FULL/DR 00:00:34 10.0.0.2 GigabitEthernet0/0
r1#
r2#sh ip eigrp neighbors
EIGRP-IPv4 Neighbors for AS(1)
H Address Interface Hold Uptime SRTT RTO Q Seq
(sec) (ms) Cnt Num
0 10.0.0.1 Gi0/0 13 00:04:07 1 200 0 45
1 20.0.0.3 Gi0/1 14 00:35:38 1 200 0 47
r2#sh ip ospf neighbor
Neighbor ID Pri State Dead Time Address Interface
33.33.33.33 1 FULL/DR 00:00:35 20.0.0.3 GigabitEthernet0/1
10.0.0.1 1 FULL/BDR 00:00:30 10.0.0.1 GigabitEthernet0/0
r2#
r3#sh ip eigrp neighbors
IP-EIGRP neighbors for process 1
H Address Interface Hold Uptime SRTT RTO Q Seq
(sec) (ms) Cnt Num
0 20.0.0.2 Fa0/0 11 00:36:02 1 300 0 17
r3#sh ip ospf neighbor
Neighbor ID Pri State Dead Time Address Interface
20.0.0.2 1 FULL/BDR 00:00:38 20.0.0.2 FastEthernet0/0
r3#
Now I create class map to match OSPF and EIGRP packets, policy map with action ‘drop & log’:
access-list 101 permit ospf any any
access-list 101 permit eigrp any any
!
class-map type inspect match-any ZBF-L2-SELF-CLASS1
match access-group 101
!
!
policy-map type inspect ZBF-L2-SELF-POLICY
class type inspect ZBF-L2-SELF-CLASS1
drop log
class class-default
drop log
!
and then security zones and zone-pairs:
zone security INSIDE
zone security OUTSIDE
zone-pair security OUT-SELF source OUTSIDE destination self
service-policy type inspect ZBF-L2-SELF-POLICY
zone-pair security SELF-OUT source self destination OUTSIDE
service-policy type inspect ZBF-L2-SELF-POLICY
!
The last step is to add interfaces to correct security zones:
!
interface GigabitEthernet0/0
zone-member security OUTSIDE
!
interface GigabitEthernet0/1
zone-member security INSIDE
!
Let’s test the applied policy:
r1#
*Apr 16 18:54:14.809: EIGRP-IPv4(1): Neighbor 20.0.0.2 not on common subnet for GigabitEthernet0/0
*Apr 16 18:54:15.749: %DUAL-5-NBRCHANGE: EIGRP-IPv4 1: Neighbor 10.0.0.2 (GigabitEthernet0/0) is down: holding time expired
*Apr 16 18:54:28.509: EIGRP-IPv4(1): Neighbor 20.0.0.3 not on common subnet for GigabitEthernet0/0
*Apr 16 18:54:33.265: %OSPF-5-ADJCHG: Process 1, Nbr 20.0.0.2 on GigabitEthernet0/0 from FULL to DOWN, Neighbor Down: Dead timer expired
r1#
r1#sh ip ospf neighbor
r1#sh ip eigrp neighbors
EIGRP-IPv4 Neighbors for AS(1)
r1#
r2(config-if)#e
*Apr 16 18:21:10.879: %FW-6-DROP_PKT: Dropping Unknown-l4 session 10.0.0.2:0 224.0.0.5:0 on zone-pair SELF-OUT class ZBF-L2-SELF-CLASS1 due to DROP action found in policy-map with ip ident 0 nd
r2#
r2#
*Apr 16 18:21:12.843: %SYS-5-CONFIG_I: Configured from console by console
*Apr 16 18:21:15.575: %FW-6-LOG_SUMMARY: 1 packet were dropped from 10.0.0.2:68 => 224.0.0.5:67 (target:class)-(SELF-OUT:ZBF-L2-SELF-CLASS1)
*Apr 16 18:21:15.575: %FW-6-LOG_SUMMARY: 2 packets were dropped from 0.0.0.0:68 => 255.255.255.255:67 (target:class)-(OUT-SELF:class-default)
*Apr 16 18:21:15.575: %FW-6-LOG_SUMMARY: 1 packet were dropped from 10.0.0.1:68 => 224.0.0.5:67 (target:class)-(OUT-SELF:ZBF-L2-SELF-CLASS1)
*Apr 16 18:21:15.575: %FW-6-LOG_SUMMARY: 1 packet were dropped from 10.0.0.1:68 => 224.0.0.10:67 (target:class)-(OUT-SELF:ZBF-L2-SELF-CLASS1)
*Apr 16 18:21:15.575: %FW-6-LOG_SUMMARY: 1 packet were dropped from 10.0.0.2:68 => 224.0.0.10:67 (target:class)-(SELF-OUT:ZBF-L2-SELF-CLASS1)
*Apr 16 18:21:15.575: %FW-6-LOG_SUMMARY: 1 packet were dropped from 20.0.0.3:0 => 224.0.0.10:0 (target:class)-(OUT-SELF:ZBF-L2-SELF-CLASS1)
*Apr 16 18:21:15.575: %FW-6-LOG_SUMMARY: 1 packet were dropped from 20.0.0.2:0 => 224.0.0.10:0 (target:class)-(OUT-SELF:ZBF-L2-SELF-CLASS1)
*Apr 16 18:21:15.575: %FW-6-LOG_SUMMARY: 1 packet were dropped from 20.0.0.3:0 => 224.0.0.5:0 (target:class)-(OUT-SELF:ZBF-L2-SELF-CLASS1)
*Apr 16 18:21:18.119: EIGRP-IPv4(1): Neighbor 10.0.0.1 not on common subnet for GigabitEthernet0/1
*Apr 16 18:21:23.315: %DUAL-5-NBRCHANGE: EIGRP-IPv4 1: Neighbor 10.0.0.1 (GigabitEthernet0/0) is down: holding time expired
r2#sh ip eigrp neighbors
EIGRP-IPv4 Neighbors for AS(1)
H Address Interface Hold Uptime SRTT RTO Q Seq
(sec) (ms) Cnt Num
1 20.0.0.3 Gi0/1 13 00:57:37 1 200 0 51
r2#sh ip ospf neighbor
Neighbor ID Pri State Dead Time Address Interface
33.33.33.33 1 FULL/DR 00:00:32 20.0.0.3 GigabitEthernet0/1
r2#
r3#sh ip eigrp neighbors
IP-EIGRP neighbors for process 1
H Address Interface Hold Uptime SRTT RTO Q Seq
(sec) (ms) Cnt Num
0 20.0.0.2 Fa0/0 12 00:58:01 1 200 0 23
r3#sh ip ospf neighbor
Neighbor ID Pri State Dead Time Address Interface
20.0.0.2 1 FULL/BDR 00:00:30 20.0.0.2 FastEthernet0/0
r3#
So, now on R2 we can’t see any adjacency between R2 and R1. You have to remember to implement ‘self’ policy in both directions: outside->self, self->outside.
You should remember following rules for self-zone:
- By default the traffic is allowed (bidirectional to and from any neighbor)
- You can either ‘drop’ or ‘pass’ the traffic, ‘inspect’ action is not valid for self-zone
- Each direction on the interface is treated separately and if you apply policy for example: OUTSIDE->SELF, the traffic from SELF to OUTSIDE is allowed without any restriction until you add the first policy
- Be careful with routing protocols and if you plan to have the policy ‘in’ and ‘out’ on self-zone, you have to permit the routing protocol explicitly
- When you work with the self-zone policy you can find that on the GNS3 some protocols are allowed despite correct configuration. I found there is a difference in processing these packet on the GNS3 and on real devices.
Useful command which allows you to see more details about dropped packets:
Device(config)# parameter-map type inspect-global
Device(config-profile)# log dropped-packets enable*
- non available on all versions of IOS
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