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doc: add discussion for a handful of nhrp commands

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Signed-off-by: Jafar Al-Gharaibeh <jafar@atcorp.com>
This commit is contained in:
Jafar Al-Gharaibeh 2019-12-17 11:03:09 -06:00
parent 73373085bc
commit 68edc5ff15
1 changed files with 78 additions and 15 deletions
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93
doc/user/nhrpd.rst
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@ -4,8 +4,8 @@
NHRP
****
*nhrpd* is an implementation of the :abbr:NHRP `(Next Hop Routing Protocol)`.
NHRP is described in :rfc`2332`.
*nhrpd* is an implementation of the :abbr:`NHRP (Next Hop Routing Protocol)`.
NHRP is described in :rfc:`2332`.
NHRP is used to improve the efficiency of routing computer network traffic over
:abbr:`NBMA (Non-Broadcast, Multiple Access)` networks. NHRP provides an
@ -13,6 +13,13 @@ ARP-like solution that allows a system to dynamically learn the NBMA address of
the other systems that are part of that network, allowing these systems to
directly communicate without requiring traffic to use an intermediate hop.
NHRP is a client-server protocol. The server side is called the :abbr:`NHS
(Next Hop Server)` or the hub, while a client is referred to as the :abbr:`NHC
(Next Hop Client)` or the spoke. When a node is configured as an NHC, it
registers its address with the NHS which keeps track of all registered spokes.
An NHC client can then query the addresses of other clients from NHS allowing
all spokes to communicate directly with each other.
Cisco Dynamic Multipoint VPN (DMVPN) is based on NHRP, and |PACKAGE_NAME| nhrpd
implements this scenario.
@ -31,7 +38,9 @@ This is similar to Cisco FlexVPN; but in contrast to opennhrp which uses
a generic subnet route.
To create NBMA GRE tunnel you might use the following (Linux terminal
commands):::
commands):
.. code-block:: console
ip tunnel add gre1 mode gre key 42 ttl 64
ip addr add 10.255.255.2/32 dev gre1
@ -68,7 +77,58 @@ command defines the GRE subnet):
Configuring NHRP
================
FIXME
.. index:: ip nhrp holdtime (1-65000)
.. clicmd:: ip nhrp holdtime (1-65000)
Holdtime is the number of seconds that have to pass before stopping to
advertise an NHRP NBMA address as valid. It also controls how often NHRP
registration requests are sent. By default registrations are sent every one
third of the holdtime.
.. index:: ip nhrp map A.B.C.D|X:X::X:X A.B.C.D|local
.. clicmd:: ip nhrp map A.B.C.D|X:X::X:X A.B.C.D|local
Map an IP address of a station to the station's NBMA address.
.. index:: ip nhrp network-id (1-4294967295)
.. clicmd:: ip nhrp network-id (1-4294967295)
Enable NHRP on this interface and set the interface's network ID. The
network ID is used to allow creating multiple nhrp domains on a router when
multiple interfaces are configured on the router. Interfaces configured
with the same ID are part of the same logical NBMA network. The ID is a
local only parameter and is not sent to other NHRP nodes and so IDs on
different nodes do not need to match. When NHRP packets are received on an
interface they are assigned to the local NHRP domain for that interface.
.. index:: ip nhrp nhs A.B.C.D nbma A.B.C.D|FQDN
.. clicmd:: ip nhrp nhs A.B.C.D nbma A.B.C.D|FQDN
Configure the Next Hop Server address and its NBMA address.
.. index:: ip nhrp nhs dynamic nbma A.B.C.D
.. clicmd:: ip nhrp nhs dynamic nbma A.B.C.D
Configure the Next Hop Server to have a dynamic address and set its NBMA
address.
.. index:: ip nhrp registration no-unique
.. clicmd:: ip nhrp registration no-unique
Allow the client to not set the unique flag in the NHRP packets. This is
useful when a station has a dynamic IP address that could change over time.
.. index:: ip nhrp shortcut
.. clicmd:: ip nhrp shortcut
Enable shortcut (spoke-to-spoke) tunnels to allow NHC to talk to each others
directly after establishing a connection without going through the hub.
.. index:: ip nhrp mtu
.. clicmd:: ip nhrp mtu
Configure NHRP advertised MTU.
.. _hub-functionality:
@ -92,25 +152,25 @@ This can be achieved with the following iptables rule.
--hashlimit-name loglimit-0 -j NFLOG --nflog-group 1 --nflog-range 128
You can fine tune the src/dstmask according to the prefix lengths you
announce internal, add additional IP range matches, or rate limitation
if needed. However, the above should be good in most cases.
You can fine tune the src/dstmask according to the prefix lengths you announce
internal, add additional IP range matches, or rate limitation if needed.
However, the above should be good in most cases.
This kernel NFLOG target's nflog-group is configured in global nhrp config
with:
.. code-block:: frr
nhrp nflog-group 1
.. index:: nhrp nflog-group (1-65535)
.. clicmd:: nhrp nflog-group (1-65535)
To start sending these traffic notices out from hubs, use the nhrp
per-interface directive:
.. code-block:: frr
interface gre1
ip nhrp redirect
.. index:: ip nhrp redirect
.. clicmd:: ip nhrp redirect
This enable redirect replies on the NHS similar to ICMP redirects except this
is managed by the nhrp protocol. This setting allows spokes to communicate with
each others directly.
.. _integration-with-ike:
@ -134,7 +194,10 @@ git repositories for the patches.
NHRP Events
===========
FIXME
.. index:: nhrp event socket SOCKET
.. clicmd:: nhrp event socket SOCKET
Configure the Unix path for the event socket.
Configuration Example
=====================