Brocade Communications Systems Layer 3 Routing Configuration ICX 6650 - Manual (Page 116)

98 Brocade ICX 6650 Layer 3 Routing Configuration Guide
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IPv4 point-to-point GRE tunnels
unicast, it is permissible for multiple tunnel interfaces to use a single loopback port. However, in
multicast, this will not allow the hardware to determine the tunnel interface that the packet was
received on in order to do an RPF check. Therefore, when IPv4 Multicast Routing is enabled on a
GRE tunnel, the tunnel interface must have a dedicated loopback port.
GRE support with other features
This section describes how GRE tunnels may affect other features on Brocade ICX 6650 devices.
Support for ECMP for routes through a GRE tunnel
Equal-Cost Multi-Path (ECMP) load sharing allows for load distribution of traffic among available
routes. When GRE is enabled, a mix of GRE tunnels and normal IP routes is supported. If multiple
routes are using GRE tunnels to a destination, packets are automatically load-balanced between
tunnels, or between tunnels and normal IP routes.
ACL, QoS, and PBR support for traffic through a GRE tunnel
PBR and ACL filtering for packets terminating on a GRE tunnel is not supported. However, PBR can
be used to map IP traffic into a GRE tunnel, but it cannot be used to route GRE traffic. QoS support
for GRE encapsulated packets is limited to copying DSCP values from the inner header onto the
outer headerTraffic coming from a tunnel can be filtered by an ACL both before and after the tunnel
is terminated and also redirected by PBR after tunnel is terminated. An ACL classifies and sets QoS
for GRE traffic. If the ACL is applied to the tunnel ingress port, then the delivery header (outer
header) would be classified or filtered before the tunnel is terminated.
NOTE
Restrictions for using ACLs in conjunction with GRE are noted in the section “Configuration
considerations for GRE IP tunnels” on page 98. PBR can be configured on tunnel loopback ports for
tunnel interfaces with no restrictions. .
Syslog messages related to GRE IP tunnels
Syslog messages provide management applications with information related to GRE IP tunnels. The
following Syslog message is supported.
Tunnel: TUN-RECURSIVE-DOWN tnnl 1, Tnl disabled due to recursive routing
Configuration considerations for GRE IP tunnels
Before configuring GRE tunnels and tunnel options, consider the configuration notes in this
section.
• When GRE is enabled on a Layer 3 switch, the following features are not supported on Virtual
Ethernet (VE) ports and VE member ports (ports that have IP addresses):
- ACL logging
- ACL statistics (also called ACL counting)
- MAC address filters
- IPv6 filters