From Perimeter Router Security Technical Implementation Guide Cisco
Part of NSAP address option not filtered
The optional and extensible natures of the IPv6 extension headers require higher scrutiny since many implementations do not always drop packets with headers that it can’t recognize and hence could cause a DoS on the target device. In addition, the type, length, value (TLV) formatting provides the ability for headers to be very large. According to the DoD IPv6 IA Guidance for MO3, headers which may be valid but serve no intended use should not be allowed into or out of any network (S0-C2-opt-3). This option type from RFC 1888 (OSI NSAPs and IPv6) has been deprecated by RFC 4048.
Review the perimeter router or multi-layer switch configuration and determine if filters are bound to the applicable interfaces to drop all inbound and outbound IPv6 packets containing a Destination Option header with option type value of 0xC3 (NSAP address). The following example will block any inbound IPv6 packet containing a Destination Option header with option type value of 0xC3 (NSAP address): interface FastEthernet0/1 description DISN CORE facing ipv6 address 2001:1:0:146::4/64 ipv6 traffic-filter IPV6_INGRESS_ACL in ! … ! ipv6 access-list IPV6-INGRESS_ACL deny 60 any any dest-option-type 195 permit ipv6 … … deny ipv6 any any or ipv6 access-list IPV6_INGRESS_ACL deny 60 any any dest-option permit ipv6 … … deny ipv6 any any Because hop-by-hop and destination options have the same exact header format, they are combined under the dest-option-type keyword. According to Cisco, since Hop-by-Hop and Destionation Option headers have non-overlapping types, you can use dest-option-type to match either. You can filter the Hop-by-Hop and Destionation Option headers via protocol 0 and 60 respectively.
Configure the perimeter router or multi-layer switch to drop all inbound and outbound IPv6 packets containing a Destination Option header with option type value of 0xC3 (NSAP address).
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