Generic Routing Encapsulation (GRE) is a network tunneling protocol developed by Cisco Systems that can encapsulate a wide variety of network layer protocols inside virtual point-to-point links or point-to-multipoint links over an Internet Protocol network. GRE tunnels also allow unicast, multicast, and broadcast traffic between routers but there is a problem with GRE tunnels it is clear text and GRE needs to provide better-grade protection. However, we can encrypt the complete GRE tunnel with IPsec security which provides good-grade security. we already configure IPsec with GRE click here. but in this blog, we will configure an IPsec with a Dynamic Virtual-Template interface.
VTI does the same job that GRE with IPsec does. They both encrypt the tunnel with IPsec. VTI removed the additional 4 bytes GRE header, thus reducing the bandwidth for sending encrypted data. VTI allows the configuration of ACL, NAT, and QoS. remember the default mode for a tunnel is GRE you have to define the mode IPsec IPv4 to configure the SVTI tunnel.
let's see the configuration- in this topology, we have head office router 1 and branch routers 3 and 4. Router 2 is acting as an internet.
Topology:-
Goal: is to make sure all the traffic is encrypted with IPsec
- Configure the topology as per the diagram
- Configure the IP addresses as per the topology
- Configure default route on head office and branch routers
- Configure crypto ISAKMP policy
- Configure crypto keyring
- Configure crypto ISAKMP profile
- Configure crypto IPsec transform-set
- Configure crypto IPsec Profile
- Configure dynamic virtual-template 1 type tunnel
- Configure EIGRP 100
- Configure tunnel 0 on branches.
- Apply the IPsec protection on the virtual tunnel
- make sure all the traffic is encrypted
- verify the configuration with show commands and ping + trace
R1(config)#interface serial 3/0
R1(config-if)#ip address 192.168.12.1 255.255.255.0
R1(config-if)#no shutdown
R1(config-if)#exit
R1(config)#interface fastethernet 0/0
R1(config-if)#ip address 192.168.10.1 255.255.255.0
R1(config-if)#no shutdown
R1(config-if)#no keepalive
R1(config-if)#exit
R1(config)#interface loopback 0
R1(config-if)#ip address 192.168.111.1 255.255.255.0
R1(config-if)#exit
R2(config-if)#ip address 192.168.12.2 255.255.255.0
R2(config-if)#no shutdown
R2(config-if)#exit
R2(config)#interface serial 3/1
R2(config-if)#ip address 192.168.23.2 255.255.255.0
R2(config-if)#no shutdown
R2(config-if)#exit
R2(config-if)#ip address 192.168.23.2 255.255.255.0
R2(config-if)#no shutdown
R2(config-if)#exit
R2(config)#interface serial 3/2
R2(config-if)#ip address 192.168.24.2 255.255.255.0
R2(config-if)#no shutdown
R2(config-if)#exit
R2(config-if)#ip address 192.168.24.2 255.255.255.0
R2(config-if)#no shutdown
R2(config-if)#exit
R3(config-if)#ip address 192.168.23.1 255.255.255.0
R3(config-if)#no shutdown
R3(config-if)#exit
R3(config)#interface fastethernet 0/0
R3(config-if)#ip address 192.168.30.1 255.255.255.0
R3(config-if)#no shutdown
R3(config-if)#no keepalive
R3(config-if)#exit
R3(config-if)#ip address 192.168.30.1 255.255.255.0
R3(config-if)#no shutdown
R3(config-if)#no keepalive
R3(config-if)#exit
R3(config)#interface loopback 0
R3(config-if)#ip address 192.168.133.1 255.255.255.0
R3(config-if)#exit
R3(config-if)#ip address 192.168.133.1 255.255.255.0
R3(config-if)#exit
R4(config-if)#ip address 192.168.24.1 255.255.255.0
R4(config-if)#no shutdown
R4(config-if)#exit
R4(config)#interface fastethernet 0/0
R4(config-if)#ip address 192.168.40.1 255.255.255.0
R4(config-if)#no shutdown
R4(config-if)#no keepalive
R4(config-if)#exit
R4(config-if)#ip address 192.168.40.1 255.255.255.0
R4(config-if)#no shutdown
R4(config-if)#no keepalive
R4(config-if)#exit
R4(config)#interface loopback 0
R4(config-if)#ip address 192.168.144.1 255.255.255.0
R4(config-if)#exit
R4(config-if)#ip address 192.168.144.1 255.255.255.0
R4(config-if)#exit
R2(config)#ip route 192.168.10.0 255.255.255.0 serial 3/0
R2(config)#ip route 192.168.30.0 255.255.255.0 serial 3/1
R2(config)#ip route 192.168.40.0 255.255.255.0 serial 3/2
R4(config)#ip route 0.0.0.0 0.0.0.0 serial 3/2
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 192.168.10.1 YES manual up up
Serial3/0 192.168.12.1 YES manual up up
Loopback0 192.168.111.1 YES manual up up
Interface IP-Address OK? Method Status Protocol
Serial3/0 192.168.12.2 YES manual up up
Serial3/1 192.168.23.2 YES manual up up
Serial3/2 192.168.24.2 YES manual up up
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 192.168.30.1 YES manual up up
Serial3/1 192.168.23.1 YES manual up up
Loopback0 192.168.133.1 YES manual up up
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 192.168.40.1 YES manual up up
Serial3/2 192.168.24.1 YES manual up up
Loopback0 192.168.144.1 YES manual up up
R1(config)#crypto isakmp policy 11
R1(config-isakmp)#authentication pre-share
R1(config-isakmp)#group 14
R1(config-isakmp)#hash sha256
R1(config-isakmp)#encryption aes 256
R1(config-isakmp)#lifetime 3600
R1(config-isakmp)#exit
R1(config-isakmp)#authentication pre-share
R1(config-isakmp)#group 14
R1(config-isakmp)#hash sha256
R1(config-isakmp)#encryption aes 256
R1(config-isakmp)#lifetime 3600
R1(config-isakmp)#exit
R1(config)#crypto keyring DVTI-KEYRING
R1(conf-keyring)#pre-shared-key address 192.168.23.1 key INTERNET
R1(conf-keyring)#pre-shared-key address 192.168.24.1 key INTERNET
R1(conf-keyring)#exit
R1(conf-keyring)#pre-shared-key address 192.168.23.1 key INTERNET
R1(conf-keyring)#pre-shared-key address 192.168.24.1 key INTERNET
R1(conf-keyring)#exit
R1(config)#crypto isakmp profile DVTI-ISAKMP
% A profile is deemed incomplete until it has match identity statements
R1(conf-isa-prof)#keyring DVTI-KEYRING
R1(conf-isa-prof)#match identity address 192.168.23.1
R1(conf-isa-prof)#match identity address 192.168.24.1
R1(conf-isa-prof)#virtual-template 1
R1(conf-isa-prof)#exit
R1(config)#crypto ipsec transform-set TRANS-SET esp-aes 256 esp-sha256-hmac
R1(cfg-crypto-trans)#mode tunnel
R1(cfg-crypto-trans)#exit
% A profile is deemed incomplete until it has match identity statements
R1(conf-isa-prof)#keyring DVTI-KEYRING
R1(conf-isa-prof)#match identity address 192.168.23.1
R1(conf-isa-prof)#match identity address 192.168.24.1
R1(conf-isa-prof)#virtual-template 1
R1(conf-isa-prof)#exit
R1(config)#crypto ipsec transform-set TRANS-SET esp-aes 256 esp-sha256-hmac
R1(cfg-crypto-trans)#mode tunnel
R1(cfg-crypto-trans)#exit
R1(config)#crypto ipsec profile DVTI-IPSEC
R1(ipsec-profile)#set transform-set TRANS-SET
R1(ipsec-profile)#exit
R1(ipsec-profile)#set transform-set TRANS-SET
R1(ipsec-profile)#exit
R1#show crypto isakmp profile
IKEv1 PROFILE DVTI-ISAKMP
Ref Count = 5
Identities matched are:
ip-address 192.168.23.1 255.255.255.255
ip-address 192.168.24.1 255.255.255.255
Certificate maps matched are:
keyring(s): DVTI-KEYRING
trustpoint(s): <all>
Ref Count = 5
Identities matched are:
ip-address 192.168.23.1 255.255.255.255
ip-address 192.168.24.1 255.255.255.255
Certificate maps matched are:
keyring(s): DVTI-KEYRING
trustpoint(s): <all>
virtual-template: 1
Transform set default: { esp-aes esp-sha-hmac }
will negotiate = { Transport, },
will negotiate = { Tunnel, },
R1#show crypto ipsec profile
IPSEC profile DVTI-IPSEC
Security association lifetime: 4608000 kilobytes/3600 seconds
Responder-Only (Y/N): N
PFS (Y/N): N
Transform sets={
TRANS-SET: { esp-256-aes esp-sha256-hmac } ,
}
Security association lifetime: 4608000 kilobytes/3600 seconds
Responder-Only (Y/N): N
PFS (Y/N): N
Transform sets={
default: { esp-aes esp-sha-hmac } ,
R3(config)#crypto isakmp policy 11
R3(config-isakmp)#authentication pre-share
R3(config-isakmp)#group 14
R3(config-isakmp)#hash sha256
R3(config-isakmp)#encryption aes 256
R3(config-isakmp)#lifetime 3600
R3(config-isakmp)#exit
R3(config-isakmp)#authentication pre-share
R3(config-isakmp)#group 14
R3(config-isakmp)#hash sha256
R3(config-isakmp)#encryption aes 256
R3(config-isakmp)#lifetime 3600
R3(config-isakmp)#exit
R3(config)#crypto keyring DVTI-KEYRING
R3(conf-keyring)#pre-shared-key address 192.168.12.1 key INTERNET
R3(conf-keyring)#exit
R3(conf-keyring)#pre-shared-key address 192.168.12.1 key INTERNET
R3(conf-keyring)#exit
R3(config)#crypto isakmp profile DVTI-ISAKMP
% A profile is deemed incomplete until it has match identity statements
R3(conf-isa-prof)#keyring DVTI-KEYRING
R3(conf-isa-prof)#match identity address 192.168.12.1
R3(config)#crypto ipsec transform-set TRANS-SET esp-aes 256 esp-sha256-hmac
R3(cfg-crypto-trans)#mode tunnel
R3(cfg-crypto-trans)#exit
% A profile is deemed incomplete until it has match identity statements
R3(conf-isa-prof)#keyring DVTI-KEYRING
R3(conf-isa-prof)#match identity address 192.168.12.1
R3(config)#crypto ipsec transform-set TRANS-SET esp-aes 256 esp-sha256-hmac
R3(cfg-crypto-trans)#mode tunnel
R3(cfg-crypto-trans)#exit
R3(config)#crypto ipsec profile DVTI-IPSEC
R3(ipsec-profile)#set transform-set TRANS-SET
R3(ipsec-profile)#exit
R3(ipsec-profile)#set transform-set TRANS-SET
R3(ipsec-profile)#exit
R3#show crypto isakmp profile
IKEv1 PROFILE DVTI-ISAKMP
Ref Count = 1
Identities matched are:
ip-address 192.168.12.1 255.255.255.255
Certificate maps matched are:
keyring(s): DVTI-KEYRING
trustpoint(s): <all>
R3#show crypto ipsec transform-set
Transform set default: { esp-aes esp-sha-hmac }
will negotiate = { Transport, },
Transform set TRANS-SET: { esp-256-aes esp-sha256-hmac }
will negotiate = { Tunnel, },
R3#show crypto ipsec profile
IPSEC profile DVTI-IPSEC
Security association lifetime: 4608000 kilobytes/3600 seconds
Responder-Only (Y/N): N
PFS (Y/N): N
Transform sets={
TRANS-SET: { esp-256-aes esp-sha256-hmac } ,
}
IPSEC profile default
Security association lifetime: 4608000 kilobytes/3600 seconds
Responder-Only (Y/N): N
PFS (Y/N): N
Transform sets={
default: { esp-aes esp-sha-hmac } ,
R4(config)#crypto isakmp policy 11
R4(config-isakmp)#authentication pre-share
R4(config-isakmp)#group 14
R4(config-isakmp)#hash sha256
R4(config-isakmp)#encryption aes 256
R4(config-isakmp)#lifetime 3600
R4(config-isakmp)#exit
R4(config-isakmp)#authentication pre-share
R4(config-isakmp)#group 14
R4(config-isakmp)#hash sha256
R4(config-isakmp)#encryption aes 256
R4(config-isakmp)#lifetime 3600
R4(config-isakmp)#exit
R4(config)#crypto keyring DVTI-KEYRING
R4(conf-keyring)#pre-shared-key address 192.168.12.1 key INTERNET
R4(conf-keyring)#exit
R4(conf-keyring)#pre-shared-key address 192.168.12.1 key INTERNET
R4(conf-keyring)#exit
R4(config)#crypto isakmp profile DVTI-ISAKMP
% A profile is deemed incomplete until it has match identity statements
R4(conf-isa-prof)#keyring DVTI-KEYRING
R4(conf-isa-prof)#match identity address 192.168.12.1
R4(conf-isa-prof)#crypto ipsec transform-set TRANS-SET esp-aes 256 esp-sha256-hmac
R4(cfg-crypto-trans)#mode tunnel
R4(cfg-crypto-trans)#exit
% A profile is deemed incomplete until it has match identity statements
R4(conf-isa-prof)#keyring DVTI-KEYRING
R4(conf-isa-prof)#match identity address 192.168.12.1
R4(conf-isa-prof)#crypto ipsec transform-set TRANS-SET esp-aes 256 esp-sha256-hmac
R4(cfg-crypto-trans)#mode tunnel
R4(cfg-crypto-trans)#exit
R4(config)#crypto ipsec profile DVTI-IPSEC
R4(ipsec-profile)#set transform-set TRANS-SET
R4(ipsec-profile)#exit
R4(ipsec-profile)#set transform-set TRANS-SET
R4(ipsec-profile)#exit
R4#show crypto isakmp profile
IKEv1 PROFILE DVTI-ISAKMP
Ref Count = 2
Identities matched are:
ip-address 192.168.12.1 255.255.255.255
Certificate maps matched are:
keyring(s): DVTI-KEYRING
trustpoint(s): <all>
R4#show crypto ipsec transform-set
Transform set default: { esp-aes esp-sha-hmac }
will negotiate = { Transport, },
Transform set TRANS-SET: { esp-256-aes esp-sha256-hmac }
will negotiate = { Tunnel, },
R4#show crypto ipsec profile
IPSEC profile DVTI-IPSEC
Security association lifetime: 4608000 kilobytes/3600 seconds
Responder-Only (Y/N): N
PFS (Y/N): N
Transform sets={
TRANS-SET: { esp-256-aes esp-sha256-hmac } ,
}
IPSEC profile default
Security association lifetime: 4608000 kilobytes/3600 seconds
Responder-Only (Y/N): N
PFS (Y/N): N
Transform sets={
default: { esp-aes esp-sha-hmac } ,
}
R1(config-if)#ip unnumbered loopback 0
R1(config-if)#tunnel source 192.168.12.1
R1(config-if)#tunnel destination dynamic
R1(config-if)#tunnel protection ipsec profile DVTI-IPSEC
R1(config-if)#no ip split-horizon eigrp 100
R1(config-if)#no ip next-hop-self eigrp 100
R1(config-if)#exit
R1(config)#router eigrp 100
R1(config-router)#network 192.168.10.0
R1(config-router)#network 192.168.111.0
R1(config-router)#no auto-summary
R1(config-router)#exit
*Apr 8 12:09:06.051: %LINEPROTO-5-UPDOWN: Line protocol on Interface Virtual-Access1, changed state to up
*Apr 8 12:09:58.035: %DUAL-5-NBRCHANGE: EIGRP-IPv4 100: Neighbor 192.168.133.1 (Virtual-Access1) is up: new adjacency
*Apr 8 12:28:57.435: %LINEPROTO-5-UPDOWN: Line protocol on Interface Virtual-Access2, changed state to up
*Apr 8 12:29:58.979: %DUAL-5-NBRCHANGE: EIGRP-IPv4 100: Neighbor 192.168.144.1 (Virtual-Access2) is up: new adjacency
R1#show interfaces virtual-template 1
Virtual-Template1 is up, line protocol is down
Hardware is Virtual Template interface
Interface is unnumbered. Using address of Loopback0 (192.168.111.1)
MTU 17916 bytes, BW 100 Kbit/sec, DLY 50000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation TUNNEL, loopback not set
Keepalive not set
Tunnel source 192.168.12.1
R1#show crypto isakmp sa
IPv4 Crypto ISAKMP SA
dst src state conn-id status
192.168.12.1 192.168.24.1 QM_IDLE 1007 ACTIVE
192.168.12.1 192.168.23.1 QM_IDLE 1006 ACTIVE
R1#show ip interface brief
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 192.168.10.1 YES manual up up
Serial3/0 192.168.12.1 YES manual up up
Loopback0 192.168.111.1 YES manual up up
Virtual-Access1 192.168.111.1 YES unset up up
Virtual-Access2 192.168.111.1 YES unset up up
Virtual-Template1 192.168.111.1 YES unset up down
R3(config)#interface tunnel 0
R3(config-if)#ip unnumbered loopback 0
R3(config-if)#tunnel source serial 3/1
R3(config-if)#tunnel destination 192.168.12.1
R3(config-if)#tunnel protection ipsec profile DVTI-IPSEC
R3(config-if)#no ip split-horizon eigrp 100
R3(config-if)#no ip next-hop-self eigrp 100
R3(config-if)#exit
R3(config)#router eigrp 100
R3(config-router)#network 192.168.30.0
R3(config-router)#network 192.168.133.0
R3(config-router)#no auto-summary
R3(config-router)#exit
*Apr 8 12:09:03.531: %CRYPTO-6-ISAKMP_ON_OFF: ISAKMP is ON
*Apr 8 12:07:48.547: %LINEPROTO-5-UPDOWN: Line protocol on Interface Tunnel0, changed state to down
*Apr 8 12:08:31.939: %LINEPROTO-5-UPDOWN: Line protocol on Interface Tunnel0, changed state to up
*Apr 8 12:09:57.203: %DUAL-5-NBRCHANGE: EIGRP-IPv4 100: Neighbor 192.168.111.1 (Tunnel0) is up: new adjacency
R4(config)#interface tunnel 0
R4(config-if)#ip unnumbered loopback 0
R4(config-if)#tunnel source 192.168.24.1
R4(config-if)#tunnel destination 192.168.12.1
R4(config-if)#tunnel protection ipsec profile DVTI-IPSEC
R4(config-if)#no ip split-horizon eigrp 100
R4(config-if)#no ip next-hop-self eigrp 100
R4(config-if)#exit
R4(config)#router eigrp 100
R4(config-router)#network 192.168.40.0
R4(config-router)#network 192.168.144.0
R4(config-router)#no auto-summary
R4(config-router)#exit
R4(config)#end
R4# show crypto isakmp sa
IPv4 Crypto ISAKMP SA
dst src state conn-id status
192.168.12.1 192.168.24.1 QM_IDLE 1003 ACTIVE
IPv6 Crypto ISAKMP SA
*Apr 8 12:28:55.243: %CRYPTO-6-ISAKMP_ON_OFF: ISAKMP is ON
*Apr 8 12:28:32.819: %LINEPROTO-5-UPDOWN: Line protocol on Interface Tunnel0, changed state to up
*Apr 8 12:29:58.335: %DUAL-5-NBRCHANGE: EIGRP-IPv4 100: Neighbor 192.168.111.1 (Tunnel0) is up: new adjacency
*Apr 8 12:26:54.647: %LINEPROTO-5-UPDOWN: Line protocol on Interface Tunnel0, changed state to down
R1#traceroute 192.168.30.1
Type escape sequence to abort.
Tracing the route to 192.168.30.1
VRF info: (vrf in name/id, vrf out name/id)
1 192.168.133.1 80 msec 60 msec 52 msec
R1#traceroute 192.168.40.1
Type escape sequence to abort.
Tracing the route to 192.168.40.1
VRF info: (vrf in name/id, vrf out name/id)
1 192.168.144.1 56 msec 60 msec 56 msec
R3#show crypto ipsec sa
interface: Tunnel0
Crypto map tag: Tunnel0-head-0, local addr 192.168.23.1
protected vrf: (none)
local ident (addr/mask/prot/port): (192.168.23.1/255.255.255.255/47/0)
remote ident (addr/mask/prot/port): (192.168.12.1/255.255.255.255/47/0)
current_peer 192.168.12.1 port 500
PERMIT, flags={origin_is_acl,}
#pkts encaps: 1487, #pkts encrypt: 1487, #pkts digest: 1487
#pkts decaps: 1498, #pkts decrypt: 1498, #pkts verify: 1498
#pkts compressed: 0, #pkts decompressed: 0
#pkts not compressed: 0, #pkts compr. failed: 0
#pkts not decompressed: 0, #pkts decompress failed: 0
#send errors 0, #recv errors 0
local crypto endpt.: 192.168.23.1, remote crypto endpt.: 192.168.12.1
path mtu 1500, ip mtu 1500, ip mtu idb Serial3/1
current outbound spi: 0xE987DEF7(3917995767)
PFS (Y/N): N, DH group: none
inbound esp sas:
spi: 0x34186AB2(874015410)
transform: esp-256-aes esp-sha256-hmac ,
in use settings ={Tunnel, }
conn id: 5, flow_id: 5, sibling_flags 80000040, crypto map: Tunnel0-head-0
sa timing: remaining key lifetime (k/sec): (4337556/3569)
IV size: 16 bytes
replay detection support: Y
Status: ACTIVE(ACTIVE)
inbound ah sas:
inbound pcp sas:
outbound esp sas:
spi: 0xE987DEF7(3917995767)
transform: esp-256-aes esp-sha256-hmac ,
in use settings ={Tunnel, }
conn id: 6, flow_id: 6, sibling_flags 80000040, crypto map: Tunnel0-head-0
sa timing: remaining key lifetime (k/sec): (4337556/3569)
IV size: 16 bytes
replay detection support: Y
Status: ACTIVE(ACTIVE)
outbound ah sas:
outbound pcp sas:
R3#show crypto isakmp sa
IPv4 Crypto ISAKMP SA
dst src state conn-id status
192.168.23.1 192.168.12.1 QM_IDLE 1002 ACTIVE
IPv6 Crypto ISAKMP SA
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