The zone-based
firewall can be deployed either on the southbound or northbound of the Locator
ID Separator Protocol (LISP) xTR device, depending on where the edge router
(routers such as Cisco ASR 1000 Aggregation Services Routers) is located in the
network. The ingress tunnel router (ITR) and egress tunnel router (ETR)
together are called the xTR device.
When the zone-based
firewall is at the northbound of the xTR device; then the firewall can view
LISP encapsulated packets, such as LISP tunneled packets, that pass through the
network.
When the zone-based
firewall is at the southbound of the xTR device, then the firewall can view the
original packet. However; the firewall is not aware of any LISP xTR processing
or do not see any LISP header. For egress packets, the xTR device does LISP
encapsulation and adds the LISP header on top of the original packet after the
firewall inspection. For ingress packets, the xTR device does LISP
decapsulation (removal of the LISP header) before the firewall inspection and
as a result, the firewall only inspects the original packet; and has no
interaction with LISP at all.
This section
describes the scenario when the zone-based firewall is deployed at the
southbound of the LISP xTR device:
If an edge router is
configured as a LISP xTR device to perform LISP encapsulation and decapsulation
functions, you can configure the zone-based firewall between the LISP interface
and the interfaces that face the LISP local endpoint identifier (EID) devices
on the same edge router. LISP header decapsulation is performed before the
header enters the zone-based firewall at the LISP interface. LISP header
encapsulation is performed after the packet egresses from the firewall at the
LISP interface. The firewall inspects only native traffic (what is native
traffic here?) in the EID space.
This section
describes the scenario when the zone-based firewall is deployed at the
northbound of the LISP xTR devicce:
If more than one
edge routers are deployed as load-sharing routers at the northbound of the xTR
device, the firewall on the edge router is considered northbound of the xTR
device. In this case, all packets that pass through the zone-based firewall are
LISP encapsulated packets. When a packet arrives, the firewall inspects either
the inner header or outer header of the LISP packets. By default, only the
outer header is inspected. You can enable inner header inspection by using the
lisp
inner-packet-inspection
command.
In Cisco IOS XE
Release, if LISP inner packet inspection is enabled, the firewall only inspects
the first fragmented inner packet, and all subsequent inner packets pass
through the firewall without further inspection. If LISP inner packet
inspection is enabled, the LISP instance ID is treated as virtual routing and
forwarding (VRF) ID, and LISP packets that belong to different instance IDs are
associated with different zone-based firewall sessions.