为Microsoft Office 365和Cisco Webex优化AnyConnect拆分隧道

简介

本文档介绍如何配置自适应安全设备(ASA)，使用设置从VPN连接中排除发往Microsoft Office 365（包括Microsoft Teams）和Cisco Webex的流量。它为支持它的AnyConnect客户端包含网络地址排除和动态(完全限定域名(FQDN))排除。

Split Tunneling

需要将ASA配置为“排除”要从隧道中排除的IPv4和IPv6目标的指定列表。遗憾的是，地址列表是动态的，可能会更改。请参阅Python脚本的配置部分和指向可用于检索列表和生成示例配置的联机python读取 — 评估 — 打印循环(REPL)的链接。

动态分割隧道

除拆分排除网络地址列表外，AnyConnect 4.6中还为Windows和Mac添加了动态拆分隧道。动态拆分隧道使用FQDN来确定连接是否应通过隧道。Python脚本还确定要添加到自定义AnyConnect属性的终端的FQDN。

配置

在Python 3 REPL中运行此脚本，或在公共REPL环境(如https://repl.it/@ministryofjay/AnyConnectO365DynamicExclude)中运行它。

import urllib.request
import uuid
import json
import re


def print_acl_lines(acl_name, ips, section_comment):
    slash_to_mask = (
        "0.0.0.0",
        "128.0.0.0",
        "192.0.0.0",
        "224.0.0.0",
        "240.0.0.0",
        "248.0.0.0",
        "252.0.0.0",
        "254.0.0.0",
        "255.0.0.0",
        "255.128.0.0",
        "255.192.0.0",
        "255.224.0.0",
        "255.240.0.0",
        "255.248.0.0",
        "255.252.0.0",
        "255.254.0.0",
        "255.255.0.0",
        "255.255.128.0",
        "255.255.192.0",
        "255.255.224.0",
        "255.255.240.0",
        "255.255.248.0",
        "255.255.252.0",
        "255.255.254.0",
        "255.255.255.0",
        "255.255.255.128",
        "255.255.255.192",
        "255.255.255.224",
        "255.255.255.240",
        "255.255.255.248",
        "255.255.255.252",
        "255.255.255.254",
        "255.255.255.255",
    )
    print(
        "access-list {acl_name} remark {comment}".format(
            acl_name=acl_name, comment=section_comment
        )
    )
    for ip in sorted(ips):
        if ":" in ip:
            # IPv6 address
            print(
                "access-list {acl_name} extended permit ip {ip} any6".format(
                    acl_name=acl_name, ip=ip
                )
            )
        else:
            # IPv4 address.  Convert to a mask
            addr, slash = ip.split("/")
            slash_mask = slash_to_mask[int(slash)]
            print(
                "access-list {acl_name} extended permit ip {addr} {mask} any4".format(
                    acl_name=acl_name, addr=addr, mask=slash_mask
                )
            )


# Fetch the current endpoints for O365
http_res = urllib.request.urlopen(
    url="https://endpoints.office.com/endpoints/worldwide?clientrequestid={}".format(
        uuid.uuid4()
    )
)
res = json.loads(http_res.read())
o365_ips = set()
o365_fqdns = set()
for service in res:
    if service["category"] == "Optimize":
        for ip in service.get("ips", []):
            o365_ips.add(ip)
        for fqdn in service.get("urls", []):
            o365_fqdns.add(fqdn)

# Generate an acl for split excluding For instance
print("##### Step 1: Create an access-list to include the split-exclude networks\n")
acl_name = "ExcludeSass"
# O365 networks
print_acl_lines(
    acl_name=acl_name,
    ips=o365_ips,
    section_comment="v4 and v6 networks for Microsoft Office 365",
)
# Microsoft Teams
# https://docs.microsoft.com/en-us/office365/enterprise/office-365-vpn-implement-split-tunnel#configuring-and-securing-teams-media-traffic
print_acl_lines(
  acl_name=acl_name,
  ips=["13.107.60.1/32"],
  section_comment="v4 address for Microsoft Teams"
)
# Cisco Webex - Per https://help.webex.com/en-us/WBX000028782/Network-Requirements-for-Webex-Teams-Services
webex_ips = [
    "64.68.96.0/19",
    "66.114.160.0/20",
    "66.163.32.0/19",
    "170.133.128.0/18",
    "173.39.224.0/19",
    "173.243.0.0/20",
    "207.182.160.0/19",
    "209.197.192.0/19",
    "216.151.128.0/19",
    "114.29.192.0/19",
    "210.4.192.0/20",
    "69.26.176.0/20",
    "62.109.192.0/18",
    "69.26.160.0/19",
]
print_acl_lines(
    acl_name=acl_name,
    ips=webex_ips,
    section_comment="IPv4 and IPv6 destinations for Cisco Webex",
)

# Edited. April 1st 2020
# Per advice from Microsoft they do NOT advise using dynamic split tunneling for their properties related to Office 365
#
print(
    "\n\n##### Step 2: Create an Anyconnect custom attribute for dynamic split excludes\n"
)
print("SKIP.  Per Microsoft as of April 2020 they advise not to dynamically split fqdn related to Office365")
#print(
#    """
#webvpn
#  anyconnect-custom-attr dynamic-split-exclude-domains description dynamic-split-exclude-domains
#
#anyconnect-custom-data dynamic-split-exclude-domains saas {}
#""".format(
#        ",".join([re.sub(r"^\*\.", "", f) for f in o365_fqdns])
#    )
#)
#
print("\n##### Step 3: Configure the split exclude in the group-policy\n")
print(
    """
group-policy GP1 attributes
 split-tunnel-policy excludespecified
 ipv6-split-tunnel-policy excludespecified
 split-tunnel-network-list value {acl_name}
""".format(
        acl_name=acl_name
    )
)

注意：Microsoft建议从VPN连接范围中排除发往关键Office 365服务的流量，方法是使用已发布的IPv4和IPv6地址范围配置分割隧道。为了获得最佳性能和最有效的VPN容量使用，应直接在VPN隧道外路由到与Office 365 Exchange Online、SharePoint Online和Microsoft Teams（在Microsoft文档中称为“优化”类别）关联的这些专用IP地址范围的流量。有关此建议的更多详细信息，请参阅使用VPN拆分隧道为远程用户优化Office 365连接。

注意：截至2020年4月初，Microsoft Teams依赖于必须从隧道中排除IP范围13.107.60.1/32。有关详细信息，请参阅配置和保护Teams媒体流量。

验证

连接用户后，他们应看到“非安全路由”(Non-Secured Routes)，其中填入了ACL中提供的地址和“动态隧道排除”(Dynamic Tunnel Exclusion)列表。