Dynamic Multipoint VPN (DMVPN)

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Revision as of 20:06, 19 August 2013 by Larena (talk | contribs) (syntax fix)
This material is work-in-progress ...

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(Last edited by Larena on 19 Aug 2013.)

http://alpinelinux.org/about under Why the Name Alpine? states: [ref?]

The first open-source implementation of Cisco's DMVPN, called OpenNHRP, was written for Alpine Linux.

So the aim of this document is to be the reference Linux DMVPN setup, with all the networking services needed for the clients that will use the DMVPN (DNS, DHCP, firewall, etc.).

Terminology

NBMA: Non-Broadcast Multi-Access network as described in RFC 2332

Hub: the Next Hop Server (NHS) performing the Next Hop Resolution Protocol service within the NBMA cloud.

Spoke: the Next Hop Resolution Protocol Client (NHC) which initiates NHRP requests of various types in order to obtain access to the NHRP service.

Tip: The recommended version of Alpine for building a DMVPN should be at minimum 2.4.11. Don't use 2.5.x, or 2.6.0 since it has in-tunnel IP fragmentation issues. Alpine 2.6.1 or later should be also okay
Note: This document assumes that all Alpine installations are run in diskless mode and that the configuration is saved on USB key

Spoke Node

A local spoke node network has support for multiple ISP connections, along with redundant layer 2 switches. At least one 802.1q capable switch is required, and a second is optional for redundancy purposes. The typical spoke node network looks like:

Alpine Setup

We will setup the network interfaces as follows:

bond0.3 = Management (not implemented below yet)
bond0.8 = LAN
bond0.64 = DMZ
bond0.80 = Voice (not implemented below yet)
bond0.96 = Internet Access Only (no access to the DMVPN network)(not implemented below yet)
bond0.256 = ISP1
bond0.257 = ISP2

Boot Alpine in diskless mode and run setup-alpine

You will be prompted something like this... Suggestion on what you could enter...
Select keyboard layout [none]: Type an appropriate layout for you
Select variant: Type an appropriate layout for you (if prompted)
Enter system hostname (short form, e.g. 'foo') [localhost]: Enter the hostname, e.g. vpnc
Available interfaces are: eth0
Enter '?' for help on bridges, bonding and vlans.
Which one do you want to initialize? (or '?' done') 		Enter bond0.8
Available bond slaves are: eth0 eth1
Which slave(s) do you want to add to bond0? (or 'done') [eth0] 		eth0 eth1
IP address for bond0? (or 'dhcp', 'none', '?') [dhcp]: Press Enter confirming 'none'
IP address for bond0.8? (or 'dhcp', 'none', '?') [dhcp]: Enter the IP address of your LAN interface, e.g. 10.1.0.1
Netmask? [255.255.255.0]: Press Enter confirming '255.255.255.0' or type another appropriate subnet mask
Gateway? (or 'none') [none]: Press Enter confirming 'none'
Do you want to do any manual network configuration? [no] yes
Make a copy of the bond0.8 configuration for bond0.64, bond0.256 and bond0.257 (optional) interfaces.
Don't forget to add a gateway and a metric value for ISP interfaces when multiple gateways are set.
Save and close the file (:wq)
DNS domain name? (e.g. 'bar.com') []: Enter the domain name of your intranet, e.g., example.net
DNS nameservers(s)? []: 8.8.8.8 8.8.4.4 (we will change them later)
Changing password for root
New password: 		Enter a secure password for the console
Retype password: Retype the above password
Which timezone are you in? ('?' for list) [UTC]: Press Enter confirming 'UTC'
HTTP/FTP proxy URL? (e.g. 'http://proxy:8080', or 'none') [none] Press Enter confirming 'none'
Enter mirror number (1-9) or URL to add (or r/f/e/done) [f]: Select a mirror close to you and press Enter
Which SSH server? ('openssh', 'dropbear' or 'none') [openssh]: Press Enter confirming 'openssh'
Which NTP client to run? ('openntpd', 'chrony' or 'none') [chrony]: Press Enter confirming 'chrony'
Which disk(s) would you like to use? (or '?' for help or 'none') [none]: Press Enter confirming 'none' or type 'none' if needed
Enter where to store configs ('floppy', 'usb' or 'none') [usb]: Press Enter confirming 'usb'
Enter apk cache directory (or '?' or 'none') [/media/usb/cache]: Press Enter confirming '/media/usb/cache'

Bonding

Update the bonding configuration: 

echo bonding mode=balance-tlb miimon=100 updelay=500 >> /etc/modules

Recursive DNS

apk add unbound

With your favorite editor open /etc/unbound/unbound.conf and add the following configuration. If you have a domain that you want unbound to resolve but is internal to your network only, the stub-zone stanza is present: 

server:
        verbosity: 1
        interface: 10.1.0.1
        do-ip4: yes
        do-ip6: no
        do-udp: yes
        do-tcp: yes
        do-daemonize: yes
        access-control: 10.1.0.0/16 allow
        access-control: 127.0.0.0/8 allow
do-not-query-localhost: no
root-hints: "/etc/unbound/named.cache"
forward-zone:
        name: "location1.example.net"
        forward-addr: 10.1.0.1
stub-zone:
	name: "example.net"
	stub-addr: 10.1.0.2
stub-zone:
	name: "example2.net"
	stub-addr: 10.1.0.2
python:
remote-control:
        control-enable: no

Fetch the latest copy of root hints:

wget http://ftp.internic.net/domain/named.cache -O /etc/unbound/named.cache

/etc/init.d/unbound start

rc-update add unbound

echo nameserver 10.1.0.1 > /etc/resolv.conf

Local DNS Zone

If you have a DNS zone that is only resolvable internally to your network, you will need a 2nd IP address on your LAN interface, and use NSD to host the zone.

First, add the following to the end of the bond0.8 stanza in /etc/network/interfaces: 

up ip addr add 10.1.0.2/24 dev bond0.8

Then, install nsd:

apk add nsd

Create /etc/nsd/nsd.conf: 

server:
        ip-address: 10.1.0.2
        port: 53
        server-count: 1
        ip4-only: yes
        hide-version: yes
        identity: ""
        zonesdir: "/etc/nsd"
zone:
        name: location1.example.net
        zonefile: location1.example.net.zone

Create zonefile in /etc/nsd/location1.example.net.zone: 

;## location1.example.net authoritative zone

$ORIGIN location1.example.net.
$TTL 86400

@ IN SOA ns1.location1.example.net. webmaster.location1.example.net. (
                2013081901      ; serial
                28800           ; refresh
                7200            ; retry
                86400           ; expire
                86400           ; min TTL
                )

                NS              ns1.location1.example.net.
                MX      10      mail.location1.example.net.
ns              IN      A       10.1.0.2
mail            IN      A       10.1.0.4

Check configuration then start:

nsd-checkconf /etc/nsd/nsd.conf

nsdc rebuild

/etc/init.d/nsd start

rc-update add nsd

GRE Tunnel

With your favorite editor open /etc/network/interfaces and add the following: 

auto gre1
iface gre1 inet static
      pre-up ip tunnel add $IFACE mode gre ttl 64 tos inherit key 12.34.56.78 || true
      address 172.16.1.1
      netmask 255.255.0.0
      post-down ip tunnel del $IFACE || true

Save and close the file.

ifup gre1

IPSEC

apk add ipsec-tools

With your favorite editor open /etc/ipsec.conf and change the content to the following: 

spdflush;
spdadd 0.0.0.0/0 0.0.0.0/0 gre -P out	ipsec esp/transport//require;
spdadd 0.0.0.0/0 0.0.0.0/0 gre -P in 	ipsec esp/transport//require;

With your favorite editor open /etc/racoon/racoon.conf and change the content to the following: 

remote anonymous {
	exchange_mode main;
	lifetime time 2 hour;
	certificate_type x509 "/etc/racoon/cert.pem" "/etc/racoon/key.pem";
	ca_type x509 "/etc/racoon/ca.pem";
	my_identifier asn1dn;
	nat_traversal on;
        script "/etc/opennhrp/racoon-ph1dead.sh" phase1_dead;
	dpd_delay 120;
	proposal {
		encryption_algorithm aes 256;
		hash_algorithm sha1;
		authentication_method rsasig;
		dh_group modp4096;
	}
	proposal {
		encryption_algorithm aes 256;
		hash_algorithm sha1;
		authentication_method rsasig;
		dh_group 2;
	}
}

sainfo anonymous {
	pfs_group 2;
	lifetime time 2 hour;
	encryption_algorithm aes 256;
	authentication_algorithm hmac_sha1;
	compression_algorithm deflate;
}

Save and close the file.

/etc/init.d/racoon start

Next Hop Resolution Protocol (NHRP)

apk add opennhrp

With your favorite editor open /etc/opennhrp/opennhrp.conf and change the content to the following: 

interface gre1
	dynamic-map 172.16.0.0/16 hub.example.com
	shortcut
	redirect
	non-caching
interface bond0.8
	shortcut-destination
interface bond0.64
	shortcut-destination

With your favorite editor open /etc/opennhrp/opennhrp-script and change the content to the following: 

#!/bin/sh

MYAS=65001

case $1 in
interface-up)
    echo "Interface $NHRP_INTERFACE is up"
    if [ "$NHRP_INTERFACE" = "gre1" ]; then
        ip route flush proto 42 dev $NHRP_INTERFACE
        ip neigh flush dev $NHRP_INTERFACE

        vtysh -d bgpd \
            -c "configure terminal" \
            -c "router bgp $MYAS" \
            -c "no neighbor core" \
            -c "neighbor core peer-group"
    fi
    ;;
peer-register)
    ;;
peer-up)
    if [ -n "$NHRP_DESTMTU" ]; then
        ARGS=`ip route get $NHRP_DESTNBMA from $NHRP_SRCNBMA | head -1`
        ip route add $ARGS proto 42 mtu $NHRP_DESTMTU
    fi
    echo "Create link from $NHRP_SRCADDR ($NHRP_SRCNBMA) to $NHRP_DESTADDR ($NHRP_DESTNBMA)"
    racoonctl establish-sa -w isakmp inet $NHRP_SRCNBMA $NHRP_DESTNBMA || exit 1
    racoonctl establish-sa -w esp inet $NHRP_SRCNBMA $NHRP_DESTNBMA gre || exit 1
    ;;
peer-down)
    echo "Delete link from $NHRP_SRCADDR ($NHRP_SRCNBMA) to $NHRP_DESTADDR ($NHRP_DESTNBMA)"
    racoonctl delete-sa isakmp inet $NHRP_SRCNBMA $NHRP_DESTNBMA
    ip route del $NHRP_DESTNBMA src $NHRP_SRCNBMA proto 42
    ;;
nhs-up)
    echo "NHS UP $NHRP_DESTADDR"
    (
        flock -x 200
        vtysh -d bgpd \
            -c "configure terminal" \
            -c "router bgp $MYAS" \
            -c "neighbor $NHRP_DESTADDR remote-as 65000" \
            -c "neighbor $NHRP_DESTADDR peer-group core" \
            -c "exit" \
            -c "exit" \
            -c "clear bgp $NHRP_DESTADDR"
    ) 200>/var/lock/opennhrp-script.lock
    ;;
nhs-down)
    (
        flock -x 200
        vtysh -d bgpd \
            -c "configure terminal" \
            -c "router bgp $MYAS" \
            -c "no neighbor $NHRP_DESTADDR"
    ) 200>/var/lock/opennhrp-script.lock
    ;;
route-up)
    echo "Route $NHRP_DESTADDR/$NHRP_DESTPREFIX is up"
    ip route replace $NHRP_DESTADDR/$NHRP_DESTPREFIX proto 42 via $NHRP_NEXTHOP dev $NHRP_INTERFACE
    ip route flush cache
    ;;
route-down)
    echo "Route $NHRP_DESTADDR/$NHRP_DESTPREFIX is down"
    ip route del $NHRP_DESTADDR/$NHRP_DESTPREFIX proto 42
    ip route flush cache
    ;;
esac

exit 0

Save and close the file. Make it executable:

chmod +x /etc/opennhrp/opennhrp-script

BGP

apk add quagga

touch /etc/quagga/zebra.conf

With your favorite editor open /etc/quagga/bgpd.conf and change the content to the following: 

password strongpassword
enable password strongpassword
log syslog

access-list 1 remark Command line access authorized IP
access-list 1 permit 127.0.0.1
line vty
 access-class 1

hostname vpnc.example.net

router bgp 65001
	bgp router-id 172.16.1.1
	network 10.1.0.0/16
	neighbor %HUB_GRE_IP% remote-as 65000
	neighbor %HUB_GRE_IP% remote-as 65000
        ...

Add lines neighbor %HUB_GRE_IP%... for each Hub host you have in your NBMA cloud.

Save and close the file.

/etc/init.d/bgpd start

Firewall

apk add awall

With your favorite editor, edit the following files and set their contents as follows:


/etc/awall/optional/params.json 

{
  "description": "params",

  "variable": {
    "B_IF" = "bond0.8",
    "C_IF" = "bond0.64",
    "E_IF" = "bond0.256",
    "E_IF2" = "bond0.257"
  }
}


/etc/awall/optional/internet-host.json 

{
  "description": "Internet host",

  "import": "params",

  "zone": {
    "E": { "iface": "$E_IF" },
    "E2": { "iface": "$E_IF2" }
  },

  "filter": [
    {
      "in": [ "E", "E2 ],
      "service": "ping",
      "action": "accept",
      "flow-limit": { "count": 10, "interval": 6 }
    },
    {
      "in": [ "E", "E2" ],
      "out": "_fw",
      "service": "ssh",
      "action": "accept",
      "conn-limit": { "count": 3, "interval": 60 }
    },

    {
      "in": "_fw",
      "out": [ "E", "E2" ],
      "service": [ "dns", "http", "ntp" ],
      "action": "accept"
    },
    {
      "in": "_fw",
      "service": [ "ping", "ssh" ],
      "action": "accept"
    }
  ]
}


/etc/awall/optional/mark.json 

{
  "description": "Mark traffic based on ISP",

  "import": [ "params", "internet-host" ],

  "route-track": [
    { "in": "E", "mark": 1 },
    { "in": "E2", "mark": 2 }
  ]
}

/etc/awall/optional/dmvpn.json 

{
  "description": "DMVPN router",

  "import": "internet-host",

  "variable": {
    "A_ADDR": [ "10.0.0.0/8", "172.16.0.0/16" ],
    "A_IF": "gre1"
  },

  "zone": {
    "A": { "addr": "$A_ADDR", "iface": "$A_IF" }
  },

  "filter": [
    { "in": [ "E", "E2" ], "out": "_fw", "service": "ipsec", "action": "accept" },
    { "in": "_fw", "out": [ "E", "E2" ], "service": "ipsec", "action": "accept" },
    {
      "in": [ "E", "E2" ],
      "out": "_fw",
      "ipsec": "in",
      "service": "gre",
      "action": "accept"
    },
    {
      "in": "_fw",
      "out": [ "E", "E2" ],
      "ipsec": "out",
      "service": "gre",
      "action": "accept"
    },

    { "in": "_fw", "out": "A", "service": "bgp", "action": "accept" },
    { "in": "A", "out": "_fw", "service": "bgp", "action": "accept"},
    { "out": [ "E", "E2" ], "dest": "$A_ADDR", "action": "reject" }
  ]
}


/etc/awall/optional/vpnc.json 

{
  "description": "VPNc",

  "import": [ "params", "internet-host", "dmvpn" ],

  "zone": {
    "B": { "iface": "$B_IF" },
    "C": { "iface": "$C_IF" }
  },


  "policy": [
    { "in": "A", "action": "accept" },
    { "in": "B", "out": "A", "action": "accept" },
    { "in": "C", "out": [ "A", "E" ], "action": "accept" },
    { "in": [ "E", "E2" ], "action": "drop" }
    { "in": "_fw", "out": "A", "action": "accept" }
  ],

  "snat": [
    { "out": [ "E", "E2" ] }
  ],

  "filter": [
    {
      "in": "A",
      "out": "_fw",
      "service": [ "ping", "ssh", "http", "https" ],
      "action": "accept"
    },

    {
      "in": [ "B", "C" ],
      "out": "_fw",
      "service": [ "dns", "ntp", "http", "https", "ssh" ],
      "action": "accept"
    },

    {
      "in": "_fw",
      "out": [ "B", "C" ],
      "service": [ "dns", "ntp" ],
      "action": "accept"
    },

    { 
      "in": [ "A", "B", "C" ],
      "out": "_fw",
      "proto": "icmp",
      "action": "accept"
    }

  ]
}

ISP Failover

apk add pingu

Configure pingu to monitor our bond0.256 and bond0.257 interfaces in /etc/pingu/pingu.conf. Add the hosts to monitor for ISP failover to /etc/pingu/pingu.conf and bind to primary ISP. We also set the ping timeout to 4 seconds.: 

timeout 4
required 2
retry 11

interface bond0.256 { 
  # route-table must correspond with mark in /etc/awall/optional/mark.json
  route-table 1
  # the rule-priority must be a higher number than the priority in /etc/shorewall/route_rules <-- FIXME
  rule-priority 20000
}

interface bond0.257 {
  # route-table must correspond with mark in /etc/awall/optional/mark.json
  route-table 2
  rule-priority 20000
}

# ping google dns via ISP1
host 8.8.8.8 {
  interval 60
  bind-interface bond0.256
}

# ping opendns via ISP1
host 208.67.222.222 {
  interval 60
  bind-interface bond0.256
}

Now, if both hosts stop responding to pings, ISP-1 will be considered down and all gateways via bond0.256 will be removed from main route table. Note that the gateway will not be removed from the route table '1'. This is so we can continue try ping via bond0.256 so we can detect that the ISP is back online. When ISP starts working again, the gateways will be added back to main route table again.

Hub Node

Troubleshooting the DMVPN

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