FlexVPN supports the use of Dynamic Routing protocols such as EIGRP, BGP and OSPF. FlexVPN also has the ability to advertise routes in the IKEv2 SA’s. In order to do this we must configure an IKEv2 Authorization Policy, this policy can be configured on the local router or centrally on a RADIUS server such as ISE.
This post only describes the steps how to configure a local IKEv2 Authorization Policy and IKEv2 Routing on a Hub and Spoke router. For further information on FlexVPN, review these blog posts Configure FlexVPN Hub and Spoke and Configure FlexVPN with certificate authentication.
Continue reading “FlexVPN IKEv2 Routing”
IKEv2 is an important protocol used in IPSec VPNs, it is used to securely authenticate peers by setting up security associations (SAs). Cisco IOS routers have predefined default encryption, integrity (hashing), DH group and PRF algorithms, some of these algorithms are no longer considered secure and therefore not recommended.
As of Cisco IOS-XE v16.8.1 the default IKEv2 Proposal will be updated, more information here: https://gblogs.cisco.com/uki/deep-dive-a-vpn-journey/
As of 2018 the recommended IKEv2 Proposal ciphers are:
Integrity: SHA512 SHA384
PRF: SHA512 SHA384
DH Group: Group19 Group 14 Group21 Group5
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In addition to Site-to-Site VPNs, FlexVPN can also be used for Remote Access VPN. It uses the same familiar commands as used to configure the S2S VPNs. Remote Access VPN can use certificate authentication (mutual certificate authentication between router and AnyConnect client), EAP (MD5/MSCHAPv2) and AnyConnect EAP. Authentication and Authorization can be performed by local AAA or external RADIUS, which can authenticate the users against Active Directory Domain and authorize depending on AD group membership.
This post will describe how to configure FlexVPN Remote Access VPN using aggregated authentication (double authentication) using AD username/password and client certificate authentication. We will not describe the basics of configuring FlexVPN Hub-and-Spoke or certificate authentication; these have been described in previous posts here:
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This post will describe how to configure FlexVPN authorization using RADIUS AAA, ISE 2.4 will be used as the RADIUS server.
The Hub router will authenticate the spoke routers with RSA certificates. The spoke routers’ certificate will have an value in the OU (organisational unit) field which will identify the location e.g. US-Branch or UK-Branch. An IKEv2 name-mangler will be used to extract the OU value from the certificate and use this in the authorization request to the RADIUS server. Depending on matching on location in the Authorization rules the RADIUS server will return different values per location.
Continue reading “FlexVPN external AAA with RADIUS”
The intention of this blog post is to describe the steps to configure certificate authentication for FlexVPN on a Cisco IOS router. This post will not describe all the steps to enrol for a certificate or all the steps to configure FlexVPN, refer to the previous blog posts list below.
The configuration used is based on the FlexVPN sVTI blog post below and has successfully enrolled for certificates on all routers. VPN connectivity has been established using PSK, the configuration below will convert from PSK to certificate authentication.
Requesting a certificate on Cisco IOS router using SCEP or manual enrolment
Configuring FlexVPN VTI and Hub-and-Spoke on Cisco routers
Configure FlexVPN for Certificate authentication
All certificates in this FlexVPN lab are signed by the CA called lab-PKI-CA
Run the command show crypto pki certificates to identify the issuer, in this instance lab-PKI-CA
Continue reading “Cisco FlexVPN with Certificate authentication”
In a FlexVPN Hub and Spoke design spoke routers are configured with a normal static VTI with the tunnel destination of the Hub’s IP address, the Hub however is configured with a Dynamic VTI. The DVTI on the Hub router is not configured with a static mapping to the peer’s IP address. The VTI on the Hub is created dynamically from a preconfigured tunnel template “virtual-template” when a tunnel is initiated by the spoke router/peer. The dynamic tunnel spawns a separate “virtual-access” interface for each spoke tunnel, inheriting the configuration from the cloned the template.
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As mentioned in the previous blog post when configuring FlexVPN configuration can be minimized by using the Smart Defaults, they comprises of default configurations for IKEv2 Proposal, IKEv2 Policy, IPSec Profile and Transform Set. This post provides a simple configuration example when using Smart Defaults and when using custom configurations.
Configuration Example – FlexVPN SVTI with Smart Defaults
This simple lab configuration is to setup a SVTI Site-to-Site VPN between 2 Cisco IOS routers.
Continue reading “Cisco FlexVPN SVTI Tunnel”